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.controller.ts

@@ -0,0 +1,16 @@
+import type { NextFunction, Request, Response } from "express";
+import { asyncHandler } from "../../shared/middlewares/index.js";
+import { healthService } from "./health.service.js";
+
+export function handleHealthCheck(
+  req: Request,
+  res: Response,
+  next: NextFunction,
+) {
+  return asyncHandler(async (req: Request, res: Response) => {
+    const verbose = req.query.verbose === "true";
+    const result = await healthService.getHealth(verbose);
+    const status = result.status === "healthy" ? 200 : 503;
+    res.status(status).json(result);
+  })(req, res, next);
+}

services/backend/src/modules/health/health.repository.ts

@@ -0,0 +1,17 @@
+import { createChildLogger } from "../../shared/logger/index.js";
+
+const logger = createChildLogger("health.repository");
+
+export class HealthRepository {
+  async checkDatabaseConnection() {
+    try {
+      // TODO: Implement actual health check
+      return { connected: true };
+    } catch (err) {
+      logger.error({ err }, "Database health check failed");
+      return { connected: false };
+    }
+  }
+}
+
+export const healthRepository = new HealthRepository();

services/backend/src/modules/health/health.schema.ts

@@ -0,0 +1,5 @@
+import { z } from "zod";
+
+export const healthCheckSchema = z.object({
+  verbose: z.coerce.boolean().optional().default(false),
+});

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();

services/backend/src/modules/health/routes/index.ts

@@ -0,0 +1,12 @@
+import type { Router } from "express";
+import express from "express";
+import { handleHealthCheck } from "../health.controller.js";
+
+export function createHealthRouter(): Router {
+  const router = express.Router();
+
+  // GET /api/health
+  router.get("/health", handleHealthCheck);
+
+  return router;
+}