chore: backend infrastructure improvements

- add URI versioning: global prefix changed to api/v1, all frontend call sites updated
- add AbortSignal.timeout to all outbound fetch calls (10s API, 15s scrapers)
- add X-Request-Id response header and requestId field in error payloads
- add response compression via @fastify/compress (gzip + brotli)
- add security headers via @fastify/helmet with CSP for the Vite SPA
- tune pg pool: max 20, idle/connection/statement timeouts on app and migration pools
- add GET /api/v1/health endpoint via @nestjs/terminus with DB connectivity check

server/package.json

@@ -26,8 +26,10 @@
   },
   "dependencies": {
     "7z-wasm": "^1.2.0",
+    "@fastify/compress": "^8.3.1",
     "@fastify/cookie": "^11.0.2",
     "@fastify/formbody": "^8.0.2",
+    "@fastify/helmet": "^13.0.2",
     "@fastify/multipart": "^9.4.0",
     "@fastify/rate-limit": "^10.3.0",
     "@fastify/static": "^9.0.0",
@@ -39,6 +41,7 @@
     "@nestjs/platform-fastify": "^11.1.14",
     "@nestjs/platform-socket.io": "^11.1.14",
     "@nestjs/schedule": "^6.1.1",
+    "@nestjs/terminus": "^11.1.1",
     "@nestjs/websockets": "^11.1.14",
     "@parcel/watcher": "^2.5.6",
     "@projectx/types": "workspace:*",