docs: update copilot instructions with strict architecture rules

.github/copilot-instructions.md

@@ -1,5 +1,10 @@
 # CaddyProxyManager+ Copilot Instructions
 
+## 🚨 CRITICAL ARCHITECTURE RULES 🚨
+- **Single Frontend Source**: All frontend code MUST reside in `frontend/`. NEVER create `backend/frontend/` or any other nested frontend directory.
+- **Single Backend Source**: All backend code MUST reside in `backend/`.
+- **No Python**: This is a Go (Backend) + React/TypeScript (Frontend) project. Do not introduce Python scripts or requirements.
+
 ## Big Picture
 - `backend/cmd/api` loads config, opens SQLite, then hands off to `internal/server` where routes from `internal/api/routes` are registered.
 - `internal/config` respects `CPM_ENV`, `CPM_HTTP_PORT`, `CPM_DB_PATH`, `CPM_FRONTEND_DIR` and creates the `data/` directory; lean on these instead of hard-coded paths.
@@ -15,15 +20,17 @@
 - Long-running work must respect the graceful shutdown flow in `server.Run(ctx)`—avoid background goroutines that ignore the context.
 
 ## Frontend Workflow
-- React 18 + Vite + React Query; start with `cd frontend && npm install && npm run dev` so Vite proxies `/api` calls to `http://localhost:8080` (configured in `vite.config.ts`).
-- Consolidate HTTP calls via `src/api/client.ts`; wrap them in hooks under `src/hooks` and expose query keys like `['proxy-hosts']` to keep cache invalidation simple.
-- Screens live in `src/pages` and render inside `components/Layout`; navigation + active styles rely on React Router + `clsx`, so extend the `links` array instead of hard-coding routes elsewhere.
-- Forms follow `pages/ProxyHosts.tsx`: local `useState` per field, submit via `useMutation`, then reset state and `invalidateQueries` for the affected list on success.
-- Styling remains a single `src/index.css` grid/aside theme; keep additions lightweight and avoid new design systems until shadcn/ui lands.
+- **Location**: Always work within `frontend/`.
+- **Stack**: React 18 + Vite + TypeScript + TanStack Query (React Query).
+- **State Management**: Use `src/hooks/use*.ts` wrapping React Query. Do not use raw `useEffect` for data fetching.
+- **API Layer**: Create typed API clients in `src/api/*.ts` that wrap `client.ts`.
+- **Development**: Run `cd frontend && npm run dev`. Vite proxies `/api` to `http://localhost:8080`.
+- **Components**: Screens live in `src/pages`. Reusable UI in `src/components`.
+- **Forms**: Use local `useState` for form fields, submit via `useMutation` from custom hooks, then `invalidateQueries` on success.
 
 ## Cross-Cutting Notes
 - Run the backend before the frontend; React Query expects the exact JSON produced by GORM tags (snake_case), so keep API and UI field names aligned.
 - When adding models, update both `internal/models` and the `AutoMigrate` call inside `internal/api/routes/routes.go`; register new Gin routes right after migrations for clarity.
 - Tests belong beside handlers (`*_test.go`); reuse the `setupTestRouter` helper structure (in-memory SQLite, Gin router, httptest requests) for fast feedback.
-- The root `Dockerfile` is still the legacy Python scaffold—do not assume it builds this stack until it is replaced with the Go/React pipeline.
-- Branch from `feature/**` and target `development`; CI currently lints/tests placeholders, so run `go test ./...` and `npm run build` locally before opening PRs.
+- The root `Dockerfile` builds the Go binary and the React static assets (multi-stage build).
+- Branch from `feature/**` and target `development`.