feat(api): add listing search caching and apply @Cacheable decorator

- Add Redis caching to SearchListingsHandler (2 min TTL, query-based key)
- Refactor GetDistrictStatsHandler to use @Cacheable decorator
- Update search-listings test to provide mock CacheService

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

apps/api/src/modules/analytics/application/queries/get-district-stats/get-district-stats.handler.ts

@@ -1,6 +1,6 @@
 import { Inject } from '@nestjs/common';
 import { QueryHandler, type IQueryHandler } from '@nestjs/cqrs';
-import { CacheService, CachePrefix, CacheTTL } from '@modules/shared';
+import { CacheService, CachePrefix, CacheTTL, Cacheable } from '@modules/shared';
 import {
   MARKET_INDEX_REPOSITORY,
   type IMarketIndexRepository,
@@ -18,20 +18,20 @@ export interface DistrictStatsDto {
 export class GetDistrictStatsHandler implements IQueryHandler<GetDistrictStatsQuery> {
   constructor(
     @Inject(MARKET_INDEX_REPOSITORY) private readonly marketIndexRepo: IMarketIndexRepository,
-    private readonly cache: CacheService,
+    private readonly cacheService: CacheService,
   ) {}
 
+  @Cacheable({
+    prefix: CachePrefix.MARKET_DISTRICT,
+    ttl: CacheTTL.DISTRICT_STATS,
+    resource: 'district_stats',
+    keyFrom: (query: unknown) => {
+      const q = query as GetDistrictStatsQuery;
+      return [q.city, q.period];
+    },
+  })
   async execute(query: GetDistrictStatsQuery): Promise<DistrictStatsDto> {
-    const cacheKey = CacheService.buildKey(CachePrefix.MARKET_DISTRICT, query.city, query.period);
-
-    return this.cache.getOrSet(
-      cacheKey,
-      async () => {
-        const districts = await this.marketIndexRepo.getDistrictStats(query.city, query.period);
-        return { city: query.city, period: query.period, districts };
-      },
-      CacheTTL.DISTRICT_STATS,
-      'district_stats',
-    );
+    const districts = await this.marketIndexRepo.getDistrictStats(query.city, query.period);
+    return { city: query.city, period: query.period, districts };
   }
 }