feat(api): add price history, Stringee SMS, Zalo OA, WebSocket notifications, and feature-listing command

- Add PriceHistory model + migration, price-changed domain event, and event handler
- Add GetPriceHistory query handler and controller endpoint
- Implement StringeeSmsService and ZaloOaService with unit tests
- Add Zalo ZNS templates for Vietnamese notification messages
- Add WebSocket notification gateway for real-time push
- Add FeatureListingCommand for promoted listings
- Apply remaining consistent-type-imports lint fixes across API modules

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

apps/api/package.json

@@ -24,10 +24,12 @@
     "@nestjs/jwt": "^11.0.2",
     "@nestjs/passport": "^11.0.5",
     "@nestjs/platform-express": "^11.0.0",
+    "@nestjs/platform-socket.io": "^11.1.19",
     "@nestjs/schedule": "^6.1.1",
     "@nestjs/swagger": "^11.2.7",
     "@nestjs/terminus": "^11.1.1",
     "@nestjs/throttler": "^6.5.0",
+    "@nestjs/websockets": "^11.1.19",
     "@paralleldrive/cuid2": "^3.3.0",
     "@prisma/adapter-pg": "^7.7.0",
     "@prisma/client": "^7.7.0",
@@ -56,6 +58,7 @@
     "reflect-metadata": "^0.2.0",
     "rxjs": "^7.8.0",
     "sanitize-html": "^2.17.2",
+    "socket.io": "^4.8.3",
     "swagger-ui-express": "^5.0.1",
     "typesense": "^3.0.5"
   },