## Implementation Complete ### Changes Made Created `backend/auth.py` with centralized JWT and password utilities: 1. **create_access_token(username: str) -> str** (auth.py:36-51) - Creates JWT tokens with 30-day expiry - Uses HS256 algorithm - Payload structure: {sub: username, exp: datetime} 2. **verify_token(token: str) -> dict | None** (auth.py:54-79) - Decodes and validates JWT tokens - Returns None for expired, invalid, or malformed tokens - No exceptions raised on failure 3. **verify_password(plain: str, hashed: str) -> bool** (auth.py:82-107) - Verifies plain text against bcrypt hash - Returns False for empty hashes or invalid formats 4. **get_password_hash(password: str) -> str** (auth.py:110-124) - Generates bcrypt hash for passwords ### Environment Configuration - JWT_SECRET_KEY loaded from environment - Default fallback for development ### Test Coverage Created backend/tests/test_auth_utils.py with 31 tests covering: - Token creation and validation - Password hashing and verification - Expired/invalid token handling - Environment variable loading - Integration tests ### Verification - All 31 new tests pass - All 379 tests in full suite pass