refactor(backend): flatten module structure, move routes to .routes.ts files

- Remove empty controllers/, services/, repositories/ subdirectories
- Move routes/index.ts into module.routes.ts (flat naming convention)
- Update imports in http/app.ts

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

services/backend/src/modules/media/media.routes.ts

@@ -0,0 +1,13 @@
+import type { Router } from "express";
+import express from "express";
+
+export function createMediaRouter(): Router {
+  const router = express.Router();
+
+  // TODO: Implement media routes
+  // GET /api/media/list
+  // POST /api/media/upload
+  // GET /api/media/:id
+
+  return router;
+}