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/src/modules/health/health.service.ts

@@ -0,0 +1,20 @@
+import { createChildLogger } from "../../shared/logger/index.js";
+import { healthRepository } from "./health.repository.js";
+
+const logger = createChildLogger("health.service");
+
+export class HealthService {
+  async getHealth(verbose = false) {
+    const dbStatus = await healthRepository.checkDatabaseConnection();
+
+    return {
+      status: dbStatus.connected ? "healthy" : "degraded",
+      timestamp: Date.now(),
+      ...(verbose && {
+        database: dbStatus,
+      }),
+    };
+  }
+}
+
+export const healthService = new HealthService();