refactor: split monolith into 3 microservices (frontend, backend, discord-gateway)

- Extract services into services/{frontend,backend,discord-gateway}
- Create packages/shared/ for shared logger, errors, utils, types
- Setup Modular MVC pattern in backend (controller→service→repository)
- Setup event-driven architecture in discord-gateway with Redis pub/sub
- Move Docker files to infra/docker/ with per-service Dockerfiles
- Update docker-compose.yml to use Traefik-only routing (no port exposes)
- Update GitHub Actions deploy workflow for multi-service matrix build
- Fix all import paths and resolve type errors across all services
- All 3 services pass tsc --noEmit clean

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/backend/package.json

@@ -0,0 +1,41 @@
+{
+  "name": "discord-moderation-backend",
+  "version": "1.0.0",
+  "description": "Backend service for Discord moderation monitoring",
+  "type": "module",
+  "main": "dist/index.js",
+  "scripts": {
+    "dev": "tsx watch src/index.ts",
+    "start": "node dist/index.js",
+    "build": "tsc",
+    "typecheck": "tsc --noEmit",
+    "lint": "biome check --diagnostic-level=error .",
+    "format": "biome format --write .",
+    "test": "vitest run"
+  },
+  "dependencies": {
+    "@discordjs/voice": "^0.19.2",
+    "@types/pg": "^8.20.0",
+    "axios": "^1.16.1",
+    "dotenv": "^17.4.2",
+    "drizzle-orm": "^0.45.2",
+    "express": "^5.2.1",
+    "helmet": "^8.1.0",
+    "ioredis": "^5.11.0",
+    "pg": "^8.21.0",
+    "pino": "^9.6.0",
+    "pino-http": "^10.3.0",
+    "prom-client": "^15.1.3",
+    "ws": "^8.20.1",
+    "zod": "^4.4.3"
+  },
+  "devDependencies": {
+    "@biomejs/biome": "latest",
+    "@types/express": "^5.0.6",
+    "@types/node": "^25.9.0",
+    "@types/ws": "^8.18.1",
+    "tsx": "^4.22.2",
+    "typescript": "^5.9.3",
+    "vitest": "latest"
+  }
+}