refactor: restructure to monorepo architecture

- Move core agent engine to packages/core/
- Add packages/types/ for shared TypeScript types
- Add packages/utils/ for utility functions
- Add apps/cli/ for command-line interface
- Add apps/gateway/ for NestJS WebSocket gateway
- Add apps/server/ for REST API server
- Restructure desktop app (electron/ → src/main/, src/preload/)
- Update pnpm workspace configuration
- Remove legacy src/ directory

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/gateway/database/database.module.ts

@@ -1,15 +0,0 @@
-/**
- * Database module for Gateway.
- *
- * Global module that provides DatabaseService to all other modules.
- */
-
-import { Global, Module } from "@nestjs/common";
-import { DatabaseService } from "./database.service.js";
-
-@Global()
-@Module({
-  providers: [DatabaseService],
-  exports: [DatabaseService],
-})
-export class DatabaseModule {}