chore: update frontend instructions

.github/copilot-instructions.md

-# Memos Project - AI Assistant Instructions
-
-## Frontend Refactoring Goal
-
-**PRIORITY**: Replace all MUI Joy UI (@mui/joy) and @usememos/mui components with shadcn/ui + Tailwind CSS v4
-
-## Key Rules
-
-1. **Replace all MUI components** with shadcn/ui + Tailwind v4
-2. **Never modify generated shadcn/ui files** from `pnpm dlx shadcn@latest add`
-3. **Use https://tweakcn.com/ for custom variants** when standard components need customization
-
-## Setup Commands
-
-```bash
-# Initialize shadcn/ui
-pnpm dlx shadcn@latest init
-
-# Add components
-pnpm dlx shadcn@latest add [component]
-```
-
-## Migration Pattern
-
-```typescript
-// OLD
-import { Button, Card, Input } from "@mui/joy";
-
-// NEW
-import { Button } from "@/components/ui/button";
-import { Card } from "@/components/ui/card";
-import { Input } from "@/components/ui/input";
-```
-
-## When Suggesting Changes
-
-- Include `pnpm dlx shadcn@latest add [component]` commands
-- Use Tailwind classes for styling
-- Mention https://tweakcn.com/ for custom variants
-- Preserve TypeScript types and accessibility
-
-## Target Files
-
-Files containing `@mui/joy` or `@usememos/mui` imports

.github/instructions/frontend.instructions.md

+## Frontend Copilot Instructions
+
+### Tech Stack
+
+- **Framework:** React + Vite
+- **UI:** shadcn/ui + Tailwind CSS v4
+- **State Management:** MobX
+- **Package Manager:** pnpm
+- **Color System:** Only use colors defined in `web/src/style.css`
+- **Component Imports:** Only via `pnpm dlx shadcn@latest add [component]`
+
+---
+
+### 💡 Guidelines
+
+✅ **Allowed:**
+
+- Use **shadcn/ui components only** (e.g., `Button`, `Input`, `Dialog`)
+- Use **Tailwind utility classes** for layout, spacing, typography
+- Use **Tailwind `bg-[var(--color-name)]`**, `text-[var(--color-name)]` referencing `web/src/style.css` for colors
+- Use **MobX for state management** (`observable`, `computed`, `action`, `useLocalObservable`)
+- Use **functional React components** with hooks
+- Use **Tailwind v4 utility classes** for responsive layouts
+
+❌ **Not Allowed:**
+
+- Do not import or use **other component libraries** (e.g., Material UI, Ant Design, Chakra)
+- Do not use **fixed color utilities** (e.g., `bg-gray-200`, `text-blue-500`)
+- Do not use **className strings with hardcoded color values**
+- Do not use **inline styles for colors**
+
+---
+
+### 🎨 Color Usage
+
+**All colors must be referenced from `web/src/style.css`**, for example:
+
+```tsx
+<div className="bg-[var(--bg-secondary)] text-[var(--text-primary)] p-4">...</div>
+```
+
+**Do not use** `bg-gray-200`, `text-gray-900`, etc.
+
+---
+
+### 📦 Adding UI Components
+
+To add new UI components, always use:
+
+```bash
+pnpm dlx shadcn@latest add [component]
+```
+
+Examples:
+
+```bash
+pnpm dlx shadcn@latest add button
+```
+
+---
+
+### 🛠️ File Structure
+
+- `web/src/components/` → shared React components
+- `web/src/pages/` → route-based pages
+- `web/src/store/v2/` → MobX stores
+- `web/src/style.css` → color variables and global styles
+- `web/src/hooks/` → reusable hooks
+
+---
+
+### 🧩 Component Development Conventions
+
+1. **Functional Components + Hooks:**
+
+   - Use `useState`, `useEffect`.
+   - Always type props with `React.FC<Props>` or explicit `Props` interfaces.
+
+2. **State:**
+
+   - Use **MobX** for shared state across components.
+   - Use local component state only for purely local UI state.
+
+3. **Styling:**
+
+   - Use Tailwind utility classes, referencing colors from `style.css`.
+   - For complex styles, extend via Tailwind plugin if needed.
+
+4. **Shadcn Integration:**
+
+   - Import components only after adding via `pnpm dlx shadcn@latest add [component]`.
+   - Do not modify the component source unless necessary; prefer composition and theming.