✨ feat(api-gateway): add Swagger, admin endpoints, and scheduler

- Add Swagger/OpenAPI documentation at /docs endpoint
- Add admin module for system-wide API key management
- Add scheduler for monthly credit reset and usage cleanup
- Add Docker Compose entry for Mac Mini deployment
- Document all endpoints with descriptions and examples

services/mana-api-gateway/src/admin/admin.module.ts

@@ -0,0 +1,10 @@
+import { Module } from '@nestjs/common';
+import { AdminController } from './admin.controller';
+import { AdminService } from './admin.service';
+
+@Module({
+	controllers: [AdminController],
+	providers: [AdminService],
+	exports: [AdminService],
+})
+export class AdminModule {}