feat: complete user-facing message and account APIs

app/gateway-api/package.json

@@ -27,6 +27,7 @@
     },
     "dependencies": {
         "@fastify/cors": "^11.2.0",
+        "@fastify/static": "^9.0.0",
         "@prisma/client": "^7.2.0",
         "@sammo-ts/common": "workspace:*",
         "@sammo-ts/game-engine": "workspace:*",
@@ -38,6 +39,7 @@
         "fastify": "^5.6.2",
         "pm2": "^5.4.3",
         "redis": "^5.10.0",
+        "sharp": "^0.34.4",
         "zod": "^4.3.5"
     }
 }