feat(api): add health check endpoints with @nestjs/terminus

Add HealthModule with /health (liveness) and /ready (readiness) probes.
Readiness checks DB (Prisma) and Redis connectivity.
Replaces the basic /health endpoint in AppController.

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

apps/api/package.json

@@ -24,6 +24,7 @@
     "@nestjs/passport": "^11.0.5",
     "@nestjs/platform-express": "^11.0.0",
     "@nestjs/swagger": "^11.2.6",
+    "@nestjs/terminus": "^11.1.1",
     "@nestjs/throttler": "^6.5.0",
     "@paralleldrive/cuid2": "^3.3.0",
     "@prisma/adapter-pg": "^7.7.0",