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

backend-api/tsconfig.build.json

@@ -0,0 +1,4 @@
+{
+  "extends": "./tsconfig.json",
+  "exclude": ["node_modules", "test", "dist", "**/*spec.ts"]
+}