build: optimize Dockerfiles for production and pin dependencies

Implement multi-stage build and static server for frontend
Run containers as non-root user and set production environment
Pin all package dependencies to exact versions

backend/package.json

@@ -13,17 +13,17 @@
     "test": "node --test --import tsx tests/*.test.ts"
   },
   "dependencies": {
-    "@fastify/cors": "latest",
-    "@fastify/multipart": "^10.0.0",
-    "@fastify/rate-limit": "^10.3.0",
-    "@fastify/static": "^9.1.3",
-    "fastify": "latest",
-    "pg": "latest"
+    "@fastify/cors": "11.2.0",
+    "@fastify/multipart": "10.0.0",
+    "@fastify/rate-limit": "10.3.0",
+    "@fastify/static": "9.1.3",
+    "fastify": "5.8.5",
+    "pg": "8.20.0"
   },
   "devDependencies": {
-    "@types/node": "latest",
-    "@types/pg": "latest",
-    "tsx": "latest",
-    "typescript": "latest"
+    "@types/node": "25.6.0",
+    "@types/pg": "8.20.0",
+    "tsx": "4.21.0",
+    "typescript": "6.0.3"
   }
 }