Add cursor rules (#9268)

Add rules for AI code editor

.cursorrules

@@ -0,0 +1,92 @@
+# Twenty Development Rules
+
+## General
+- Twenty is an open source CRM built with Typescript (React, NestJS)
+
+### Main Packages / folders
+- packages/twenty-front: Main Frontend (React)
+- packages/twenty-server: Main Backend (NestJS)
+- packages/twenty-website: Marketing website + docs (NextJS)
+- packages/twenty-ui: UI library (React)
+- packages/twenty-shared: Shared utils, constants, types
+
+### Development Stack
+- Package Manager: yarn
+- Monorepo: nx
+- Database: PostgreSQL + TypeORM (core, metadata schemas)
+- State Management: Recoil
+- Data Management: Apollo / GraphQL
+- Cache: redis
+- Auth: JWT
+- Queue: BullMQ
+- Storage: S3/local filesystem
+- Testing Backend: Jest, Supertest
+- Testing Frontend: Jest, Storybook, MSW
+- Testing E2E: Playwright
+
+## Styling
+- Use @emotion/styled, never CSS classes/Tailwind
+- Prefix styled components with 'Styled'
+- Keep styled components at top of file
+- Use Theme object for colors/spacing/typography
+- Use Theme values instead of px/rem
+- Use mq helper for media queries
+
+## TypeScript
+- No 'any' type - use proper typing
+- Use type over interface
+- String literals over enums (except GraphQL)
+- Props suffix for component props types
+- Use type inference when possible
+- Enable strict mode and noImplicitAny
+
+## React
+- Only functional components
+- Named exports only
+- No useEffect, prefer event handlers
+- Small focused components
+- Proper prop naming (onClick, isActive)
+- Destructure props with types
+
+## State Management
+- Recoil for global state
+- Apollo Client for GraphQL/server state
+- Atoms in states/ directory
+- Multiple small atoms over prop drilling
+- No useRef for state
+- Extract data fetching to siblings
+- useRecoilValue/useRecoilState appropriately
+
+## File Structure
+- One component per file
+- Features in modules/
+- Hooks in hooks/
+- States in states/
+- Types in types/
+- PascalCase components, camelCase others
+
+## Code Style
+- Early returns
+- No nested ternaries
+- No else-if
+- Optional chaining over &&
+- Small focused functions
+- Clear variable names
+- No console.logs in commits
+- Few comments, prefer code readability
+
+## GraphQL
+- Use gql tag
+- Separate operation files
+- Proper codegen typing
+- Consistent naming (getX, updateX)
+- Use fragments
+- Use generated types
+
+## Testing
+- Test every feature
+- React Testing Library
+- Test behavior not implementation
+- Mock external deps
+- Use data-testid
+- Follow naming conventions

.vscode/settings.json

@@ -46,4 +46,7 @@
     "**/.yarn": true,
   },
   "eslint.debug": true,
+  "files.associations": {
+    ".cursorrules": "markdown"
+  }
 }