Claude Code Prompt Enhancer

Add a user profile API endpoint to the Express backend. **Endpoint:** GET /api/users/:id/profile **Requirements:** - Return user profile data (name, email, avatar, bio, joinedAt) - Exclude sensitive fields (password, tokens) - Return 404 if user not found - Require authentication (use existing auth middleware) - Add input validation for the user ID parameter **Follow existing patterns:** - Look at /api/users/me for similar endpoint structure - Use the existing User model and error handling - Add to the existing users router file **After implementation:** - Add tests following the pattern in /tests/api/ - Update the API documentation if it exists Please commit with a descriptive message when done.