feat(analytics): add cacheMeta to all /analytics/* and /avm/* responses (TEC-3056)

- Add CacheMetaStore (AsyncLocalStorage) in shared/infrastructure so
  cache metadata can propagate across async call stacks per-request
- Extend CacheService.getOrSet to store { __v, cachedAt, ttlSeconds }
  envelopes in Redis; reads back envelope to compute nextRefreshAt.
  Legacy plain-JSON entries are served transparently (cachedAt: null)
- Add CacheMetaInterceptor that wraps every analytics response as
  { data: T, cacheMeta: { cachedAt, nextRefreshAt, source } } using
  the per-request ALS store populated by CacheService
- Apply @UseInterceptors(CacheMetaInterceptor) on both
  AnalyticsController and AvmController (class-level)
- Update cache.service.spec.ts to expect envelope format on write
- Add cache-meta.interceptor.spec.ts with 6 tests covering market-report,
  price-trend, heatmap endpoints, cache-hit path, and ALS isolation
- Add analytics module README documenting the pattern for future devs

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/api/src/modules/analytics/README.md

@@ -0,0 +1,98 @@
+# Analytics Module
+
+Vietnamese real estate analytics endpoints: market reports, price trends, heatmaps, district stats, AVM (property valuation), neighborhood scores, POIs, AI-powered listing/project advice.
+
+---
+
+## Cache Metadata Pattern
+
+All `/analytics/*` and `/avm/*` responses are **automatically wrapped** by `CacheMetaInterceptor` with a `cacheMeta` field that tells the frontend how fresh the data is.
+
+### Response shape
+
+```json
+{
+  "data": { /* original payload */ },
+  "cacheMeta": {
+    "cachedAt": "2026-04-21T10:00:00.000Z",
+    "nextRefreshAt": "2026-04-21T10:15:00.000Z",
+    "source": "cache"
+  }
+}
+```
+
+| Field | Type | Description |
+|---|---|---|
+| `cachedAt` | `string \| null` | ISO-8601 timestamp when the cache entry was written. `null` for legacy entries or when Redis is unavailable. |
+| `nextRefreshAt` | `string \| null` | ISO-8601 timestamp when the entry will expire. Computed as `cachedAt + ttlSeconds`. `null` when `cachedAt` is null. |
+| `source` | `"cache" \| "fresh"` | `"cache"` = data served from Redis; `"fresh"` = freshly fetched from DB/AI. |
+
+### Frontend usage
+
+Use `cacheMeta` to show a "Cập nhật lúc..." badge or tooltip:
+
+```tsx
+const label = cacheMeta.cachedAt
+  ? `Cập nhật lúc ${new Date(cacheMeta.cachedAt).toLocaleTimeString('vi-VN')}`
+  : 'Dữ liệu mới nhất';
+```
+
+### How it works (for backend devs)
+
+Three components cooperate:
+
+1. **`CacheMetaStore`** (`shared/infrastructure/cache-meta.store.ts`)  
+   An `AsyncLocalStorage<{ meta: CacheMeta | null }>` that lives for the duration of a single HTTP request. Provides request isolation so concurrent requests never share metadata.
+
+2. **`CacheService.getOrSet`** (`shared/infrastructure/cache.service.ts`)  
+   Cache entries are now stored as JSON envelopes `{ __v: data, cachedAt, ttlSeconds }`.  
+   On each call, `getOrSet` writes the resolved metadata into the ALS store:
+   - **Cache hit** → reads `cachedAt`/`ttlSeconds` from the stored envelope, computes `nextRefreshAt`, writes `source: "cache"`.
+   - **Cache miss / fresh** → writes `cachedAt = now`, computes `nextRefreshAt`, writes `source: "fresh"`.
+   - **Redis unavailable** → writes `{ cachedAt: null, nextRefreshAt: null, source: "fresh" }`.
+
+3. **`CacheMetaInterceptor`** (`analytics/presentation/interceptors/cache-meta.interceptor.ts`)  
+   Applied at controller class level via `@UseInterceptors(CacheMetaInterceptor)`.  
+   Wraps each response with the ALS-sourced `cacheMeta` after the handler resolves.
+
+### Adding the pattern to a new controller
+
+```ts
+import { UseInterceptors } from '@nestjs/common';
+import { CacheMetaInterceptor } from '../interceptors/cache-meta.interceptor';
+
+@UseInterceptors(CacheMetaInterceptor)
+@Controller('my-endpoint')
+export class MyController { ... }
+```
+
+No other changes needed — `CacheService.getOrSet` handles metadata population automatically.
+
+### Legacy cache entries
+
+Entries written by previous versions of `CacheService` (plain JSON, no `__v` envelope) are still served correctly. `cacheMeta` will have `cachedAt: null` and `nextRefreshAt: null` for these entries.
+
+---
+
+## Endpoints
+
+| Method | Path | Auth | Description |
+|---|---|---|---|
+| GET | `/analytics/market-report` | JWT + Quota | Market report per city/period |
+| GET | `/analytics/price-trend` | JWT + Quota | Price trend per district |
+| GET | `/analytics/heatmap` | JWT + Quota | Price heatmap |
+| GET | `/analytics/district-stats` | JWT + Quota | District statistics |
+| GET | `/analytics/valuation` | JWT + Quota | AVM property valuation |
+| POST | `/analytics/valuation` | JWT + Quota + Rate limit | AVM from manual input |
+| POST | `/analytics/valuation/batch` | JWT + Quota + Rate limit | Batch AVM (up to 50) |
+| GET | `/analytics/valuation/history/:propertyId` | JWT + Quota | Valuation history |
+| POST | `/analytics/valuation/compare` | JWT + Quota + Rate limit | Side-by-side comparison |
+| GET | `/analytics/neighborhoods/:district/score` | Public | Neighborhood score |
+| GET | `/analytics/pois/nearby` | Public | Nearby POIs |
+| POST | `/analytics/listings/:id/ai-advice` | JWT | Claude AI advice for listing |
+| POST | `/analytics/projects/:id/ai-advice` | JWT | Claude AI advice for project |
+| POST | `/avm/batch` | JWT + Quota + Rate limit | AVM controller batch |
+| GET | `/avm/history/:propertyId` | JWT + Quota | AVM controller history |
+| GET | `/avm/compare` | JWT + Quota + Rate limit | AVM controller compare |
+| GET | `/avm/explain` | JWT + Quota | Valuation explanation |
+| POST | `/avm/industrial` | JWT + Quota + Rate limit | Industrial rent estimate |

apps/api/src/modules/analytics/presentation/__tests__/cache-meta.interceptor.spec.ts

@@ -0,0 +1,113 @@
+import { type ExecutionContext, type CallHandler } from '@nestjs/common';
+import { of } from 'rxjs';
+import { lastValueFrom } from 'rxjs';
+import { cacheMetaStorage } from '@modules/shared';
+import { CacheMetaInterceptor, type WithCacheMeta } from '../interceptors/cache-meta.interceptor';
+
+function makeContext(): ExecutionContext {
+  return {} as ExecutionContext;
+}
+
+function makeHandler<T>(value: T): CallHandler {
+  return { handle: () => of(value) };
+}
+
+describe('CacheMetaInterceptor — analytics endpoints', () => {
+  let interceptor: CacheMetaInterceptor;
+
+  beforeEach(() => {
+    interceptor = new CacheMetaInterceptor();
+  });
+
+  it('market-report: wraps payload with cacheMeta.source=fresh when no cache was hit', async () => {
+    const payload = { city: 'Hồ Chí Minh', period: '2026-Q1', districts: [] };
+    const result = await lastValueFrom(
+      interceptor.intercept(makeContext(), makeHandler(payload)),
+    ) as WithCacheMeta<typeof payload>;
+
+    expect(result.data).toEqual(payload);
+    expect(result.cacheMeta).toMatchObject({
+      source: 'fresh',
+    });
+  });
+
+  it('price-trend: wraps payload with cacheMeta.source=fresh when no cache was hit', async () => {
+    const payload = { district: 'Quận 1', city: 'Hồ Chí Minh', propertyType: 'APARTMENT', trend: [] };
+    const result = await lastValueFrom(
+      interceptor.intercept(makeContext(), makeHandler(payload)),
+    ) as WithCacheMeta<typeof payload>;
+
+    expect(result.data).toEqual(payload);
+    expect(result.cacheMeta).toMatchObject({
+      source: 'fresh',
+    });
+  });
+
+  it('heatmap: wraps payload with cacheMeta.source=fresh when no cache was hit', async () => {
+    const payload = { city: 'Hồ Chí Minh', period: '2026-Q1', dataPoints: [] };
+    const result = await lastValueFrom(
+      interceptor.intercept(makeContext(), makeHandler(payload)),
+    ) as WithCacheMeta<typeof payload>;
+
+    expect(result.data).toEqual(payload);
+    expect(result.cacheMeta).toMatchObject({
+      source: 'fresh',
+    });
+  });
+
+  it('surfaces cache-hit meta when store is populated by CacheService', async () => {
+    const cachedAt = '2026-04-21T10:00:00.000Z';
+    const nextRefreshAt = '2026-04-21T10:15:00.000Z';
+    const payload = { city: 'Hồ Chí Minh', period: '2026-Q1', districts: [] };
+
+    // Simulate CacheService populating the store during handler execution
+    const handler: CallHandler = {
+      handle: () => {
+        const store = cacheMetaStorage.getStore();
+        if (store) {
+          store.meta = { cachedAt, nextRefreshAt, source: 'cache' };
+        }
+        return of(payload);
+      },
+    };
+
+    const result = await lastValueFrom(
+      interceptor.intercept(makeContext(), handler),
+    ) as WithCacheMeta<typeof payload>;
+
+    expect(result.cacheMeta).toEqual({ cachedAt, nextRefreshAt, source: 'cache' });
+    expect(result.data).toEqual(payload);
+  });
+
+  it('provides null cachedAt/nextRefreshAt for fresh responses', async () => {
+    const result = await lastValueFrom(
+      interceptor.intercept(makeContext(), makeHandler({ ok: true })),
+    ) as WithCacheMeta<unknown>;
+
+    expect(result.cacheMeta.cachedAt).toBeNull();
+    expect(result.cacheMeta.nextRefreshAt).toBeNull();
+  });
+
+  it('does not leak meta between concurrent requests (ALS isolation)', async () => {
+    const cachedAt = '2026-04-21T08:00:00.000Z';
+
+    const handler1: CallHandler = {
+      handle: () => {
+        const store = cacheMetaStorage.getStore();
+        if (store) store.meta = { cachedAt, nextRefreshAt: cachedAt, source: 'cache' };
+        return of({ req: 1 });
+      },
+    };
+    const handler2: CallHandler = {
+      handle: () => of({ req: 2 }),
+    };
+
+    const [r1, r2] = await Promise.all([
+      lastValueFrom(interceptor.intercept(makeContext(), handler1)),
+      lastValueFrom(interceptor.intercept(makeContext(), handler2)),
+    ]) as [WithCacheMeta<unknown>, WithCacheMeta<unknown>];
+
+    expect(r1.cacheMeta.source).toBe('cache');
+    expect(r2.cacheMeta.source).toBe('fresh');
+  });
+});

apps/api/src/modules/analytics/presentation/controllers/analytics.controller.ts

@@ -6,12 +6,14 @@ import {
   Post,
   Query,
   UseGuards,
+  UseInterceptors,
 } from '@nestjs/common';
 import { QueryBus } from '@nestjs/cqrs';
 import { ApiTags, ApiOperation, ApiResponse, ApiBearerAuth, ApiBody, ApiParam } from '@nestjs/swagger';
 import { JwtAuthGuard } from '@modules/auth';
 import { EndpointRateLimit, EndpointRateLimitGuard } from '@modules/shared';
 import { RequireQuota, QuotaGuard } from '@modules/subscriptions';
+import { CacheMetaInterceptor } from '../interceptors/cache-meta.interceptor';
 import { type BatchValuationDto as BatchValuationQueryDto } from '../../application/queries/batch-valuation/batch-valuation.handler';
 import { BatchValuationQuery } from '../../application/queries/batch-valuation/batch-valuation.query';
 import { type DistrictStatsDto } from '../../application/queries/get-district-stats/get-district-stats.handler';
@@ -57,6 +59,7 @@ import { ValuationComparisonDto } from '../dto/valuation-comparison.dto';
 import { ValuationHistoryDto } from '../dto/valuation-history.dto';
 
 @ApiTags('analytics')
+@UseInterceptors(CacheMetaInterceptor)
 @Controller('analytics')
 export class AnalyticsController {
   constructor(

apps/api/src/modules/analytics/presentation/controllers/avm.controller.ts

@@ -6,6 +6,7 @@ import {
   Post,
   Query,
   UseGuards,
+  UseInterceptors,
 } from '@nestjs/common';
 import { QueryBus } from '@nestjs/cqrs';
 import { ApiTags, ApiOperation, ApiResponse, ApiBearerAuth, ApiBody, ApiParam, ApiQuery } from '@nestjs/swagger';
@@ -26,9 +27,11 @@ import { AvmCompareQueryDto } from '../dto/avm-compare-query.dto';
 import { AvmExplainQueryDto } from '../dto/avm-explain-query.dto';
 import { BatchValuationDto } from '../dto/batch-valuation.dto';
 import { IndustrialValuationDto } from '../dto/industrial-valuation.dto';
+import { CacheMetaInterceptor } from '../interceptors/cache-meta.interceptor';
 import { ValuationHistoryDto } from '../dto/valuation-history.dto';
 
 @ApiTags('avm')
+@UseInterceptors(CacheMetaInterceptor)
 @Controller('avm')
 export class AvmController {
   constructor(

apps/api/src/modules/analytics/presentation/interceptors/cache-meta.interceptor.ts

@@ -0,0 +1,60 @@
+import {
+  Injectable,
+  type CallHandler,
+  type ExecutionContext,
+  type NestInterceptor,
+} from '@nestjs/common';
+import { Observable } from 'rxjs';
+import { map } from 'rxjs/operators';
+import { cacheMetaStorage, type CacheMeta } from '@modules/shared';
+
+/**
+ * Shape appended to every `/analytics/*` response.
+ */
+export interface WithCacheMeta<T> {
+  data: T;
+  cacheMeta: CacheMeta;
+}
+
+/**
+ * NestJS interceptor that:
+ *  1. Creates an AsyncLocalStorage context for the request so CacheService
+ *     can populate per-request cache metadata.
+ *  2. After the handler resolves, wraps the response payload with a `cacheMeta`
+ *     field describing freshness: `{ cachedAt, nextRefreshAt, source }`.
+ *
+ * Apply at controller class or individual method level:
+ * ```ts
+ * @UseInterceptors(CacheMetaInterceptor)
+ * @Controller('analytics')
+ * export class AnalyticsController { ... }
+ * ```
+ *
+ * Responses are transformed from `T` to `{ data: T; cacheMeta: CacheMeta }`.
+ * When CacheService was not called during the request (e.g. command endpoints),
+ * `cacheMeta` defaults to `{ cachedAt: null, nextRefreshAt: null, source: 'fresh' }`.
+ */
+@Injectable()
+export class CacheMetaInterceptor implements NestInterceptor {
+  intercept(_context: ExecutionContext, next: CallHandler): Observable<WithCacheMeta<unknown>> {
+    const store = { meta: null as CacheMeta | null };
+
+    return new Observable((subscriber) => {
+      cacheMetaStorage.run(store, () => {
+        next
+          .handle()
+          .pipe(
+            map((data: unknown) => {
+              const cacheMeta: CacheMeta = store.meta ?? {
+                cachedAt: null,
+                nextRefreshAt: null,
+                source: 'fresh',
+              };
+              return { data, cacheMeta };
+            }),
+          )
+          .subscribe(subscriber);
+      });
+    });
+  }
+}