initial: Backend Auth Module + Design System + Complete Documentation

- Setup NestJS with TypeScript, ConfigModule, JWT authentication
- Implemented Auth Module with signup, login, logout endpoints
- Created DTOs with validation (SignupDto, LoginDto)
- JWT Strategy with Passport integration for token validation
- JwtAuthGuard for route protection with Bearer tokens
- CurrentUser decorator for dependency injection
- Supabase integration for user management and auth
- Complete API documentation (API.md) with all endpoints
- Design System for Web (Next.js + Tailwind) and Mobile (Flutter)
- Comprehensive project documentation and roadmap
- Environment configuration with Joi schema validation
- Ready for Tasks Module and RLS implementation

frontend-next/public/file.svg

@@ -0,0 +1 @@
+<svg fill="none" viewBox="0 0 16 16" xmlns="http://www.w3.org/2000/svg"><path d="M14.5 13.5V5.41a1 1 0 0 0-.3-.7L9.8.29A1 1 0 0 0 9.08 0H1.5v13.5A2.5 2.5 0 0 0 4 16h8a2.5 2.5 0 0 0 2.5-2.5m-1.5 0v-7H8v-5H3v12a1 1 0 0 0 1 1h8a1 1 0 0 0 1-1M9.5 5V2.12L12.38 5zM5.13 5h-.62v1.25h2.12V5zm-.62 3h7.12v1.25H4.5zm.62 3h-.62v1.25h7.12V11z" clip-rule="evenodd" fill="#666" fill-rule="evenodd"/></svg>