feat(cache): implement Redis caching layer for hot-read endpoints

Add cache-aside pattern for listing detail, search results, market
analytics (4 endpoints), and user profile queries. Cache invalidation
on all write mutations. Prometheus cache_hit_total/cache_miss_total
metrics with resource labels.

- CacheService: getOrSet, invalidate, invalidateByPrefix (SCAN-based)
- TTLs: listing 5m, search 1m, market 30m, profile 10m
- All 230 tests passing (13 new cache tests + 6 updated handler tests)

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

apps/api/src/modules/search/application/queries/search-properties/search-properties.handler.ts

@@ -1,5 +1,6 @@
 import { type IQueryHandler, QueryHandler } from '@nestjs/cqrs';
 import { Inject } from '@nestjs/common';
+import { CacheService, CachePrefix, CacheTTL } from '@modules/shared/infrastructure/cache.service';
 import { SearchPropertiesQuery } from './search-properties.query';
 import {
   SEARCH_REPOSITORY,
@@ -11,6 +12,7 @@ import {
 export class SearchPropertiesHandler implements IQueryHandler<SearchPropertiesQuery> {
   constructor(
     @Inject(SEARCH_REPOSITORY) private readonly searchRepo: ISearchRepository,
+    private readonly cache: CacheService,
   ) {}
 
   async execute(query: SearchPropertiesQuery): Promise<SearchResult> {
@@ -46,12 +48,36 @@ export class SearchPropertiesHandler implements IQueryHandler<SearchPropertiesQu
       filters.push(`city:=${query.city}`);
     }
 
-    return this.searchRepo.search({
+    const searchParams = {
       query: query.query,
       filterBy: filters.join(' && '),
       sortBy: query.sortBy,
       page: query.page,
       perPage: query.perPage,
-    });
+    };
+
+    const cacheKey = CacheService.buildKey(
+      CachePrefix.SEARCH,
+      query.query ?? '*',
+      query.propertyType,
+      query.transactionType,
+      query.district,
+      query.city,
+      query.page,
+      query.perPage,
+      query.priceMin,
+      query.priceMax,
+      query.areaMin,
+      query.areaMax,
+      query.bedrooms,
+      query.sortBy,
+    );
+
+    return this.cache.getOrSet(
+      cacheKey,
+      () => this.searchRepo.search(searchParams),
+      CacheTTL.SEARCH_RESULTS,
+      'search',
+    );
   }
 }