chore(iios): production Dockerfile + migrate entrypoint + env/secrets contract

Adds a multi-stage Dockerfile for iios-service (build → pnpm deploy prune →
slim non-root runtime), a docker-entrypoint that runs `prisma migrate deploy`
then starts the server as PID 1, a .dockerignore, a fully-commented
.env.example config contract, and docs/DEPLOYMENT.md (topology, scaling,
release strategy, prod-readiness gaps). Moves prisma to dependencies so the
CLI ships in the prod bundle. Image builds, migrates, and serves /health 200.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/iios-service/package.json

@@ -20,6 +20,7 @@
     "@nestjs/platform-socket.io": "^11.1.27",
     "@nestjs/websockets": "^11.1.27",
     "@prisma/client": "^6.2.1",
+    "prisma": "^6.2.1",
     "socket.io": "^4.8.3",
     "class-transformer": "^0.5.1",
     "class-validator": "^0.15.1",
@@ -35,7 +36,6 @@
     "@types/express": "^5.0.6",
     "@types/jsonwebtoken": "^9.0.10",
     "@types/node": "^26.0.1",
-    "prisma": "^6.2.1",
     "socket.io-client": "^4.8.3",
     "typescript": "^5.7.3"
   }