Fix CI failures: add backend/conftest.py for module resolution and run black formatting

- Add backend/conftest.py that inserts the backend directory into sys.path,
  fixing ModuleNotFoundError when pytest runs from the backend/ directory
  (as CI does with `cd backend && pytest tests/`)
- Run black formatter on all 28 backend files that needed reformatting
- All 53 tests pass with both `pytest tests/` and `python -m pytest tests/`

Co-authored-by: christianlouis <361235+christianlouis@users.noreply.github.com>
Agent-Logs-Url: https://github.com/christianlouis/pop_puller_to_gmail/sessions/beb47db2-da25-416a-8fb0-c1452a3b22a7

backend/app/core/security.py

@@ -1,6 +1,7 @@
 """
 Security utilities for encryption, hashing, and token generation.
 """
+
 import hashlib
 import secrets
 from datetime import datetime, timedelta
@@ -14,7 +15,6 @@ import base64
 
 from app.core.config import settings
 
-
 # Password hashing context
 pwd_context = CryptContext(schemes=["bcrypt"], deprecated="auto")
 
@@ -29,17 +29,23 @@ def get_password_hash(password: str) -> str:
     return pwd_context.hash(password)
 
 
-def create_access_token(data: Dict[str, Any], expires_delta: Optional[timedelta] = None) -> str:
+def create_access_token(
+    data: Dict[str, Any], expires_delta: Optional[timedelta] = None
+) -> str:
     """Create JWT access token"""
     to_encode = data.copy()
-    
+
     if expires_delta:
         expire = datetime.utcnow() + expires_delta
     else:
-        expire = datetime.utcnow() + timedelta(minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES)
-    
+        expire = datetime.utcnow() + timedelta(
+            minutes=settings.ACCESS_TOKEN_EXPIRE_MINUTES
+        )
+
     to_encode.update({"exp": expire, "type": "access"})
-    encoded_jwt = jwt.encode(to_encode, settings.SECRET_KEY, algorithm=settings.ALGORITHM)
+    encoded_jwt = jwt.encode(
+        to_encode, settings.SECRET_KEY, algorithm=settings.ALGORITHM
+    )
     return encoded_jwt
 
 
@@ -48,14 +54,18 @@ def create_refresh_token(data: Dict[str, Any]) -> str:
     to_encode = data.copy()
     expire = datetime.utcnow() + timedelta(days=settings.REFRESH_TOKEN_EXPIRE_DAYS)
     to_encode.update({"exp": expire, "type": "refresh"})
-    encoded_jwt = jwt.encode(to_encode, settings.SECRET_KEY, algorithm=settings.ALGORITHM)
+    encoded_jwt = jwt.encode(
+        to_encode, settings.SECRET_KEY, algorithm=settings.ALGORITHM
+    )
     return encoded_jwt
 
 
 def decode_token(token: str) -> Optional[Dict[str, Any]]:
     """Decode and validate JWT token"""
     try:
-        payload = jwt.decode(token, settings.SECRET_KEY, algorithms=[settings.ALGORITHM])
+        payload = jwt.decode(
+            token, settings.SECRET_KEY, algorithms=[settings.ALGORITHM]
+        )
         return payload
     except JWTError:
         return None
@@ -68,27 +78,27 @@ def generate_random_token(length: int = 32) -> str:
 
 class CredentialEncryption:
     """Handles encryption/decryption of sensitive credentials (POP3/IMAP passwords)"""
-    
+
     def __init__(self, key: Optional[str] = None, user_id: Optional[int] = None):
         """
         Initialize encryption with a key.
         If no key provided, uses the one from settings.
         In production, use a unique salt per user for enhanced security.
-        
+
         Args:
             key: Encryption key (defaults to settings.ENCRYPTION_KEY)
             user_id: Optional user ID for per-user salt generation
         """
         if key is None:
             key = settings.ENCRYPTION_KEY
-        
+
         # Generate salt - unique per user for enhanced security
         if user_id is not None:
-            salt = hashlib.sha256(f'pop3fwd_usr_{user_id}'.encode()).digest()[:16]
+            salt = hashlib.sha256(f"pop3fwd_usr_{user_id}".encode()).digest()[:16]
         else:
             # Default salt for system-wide operations (use with caution)
-            salt = b'pop3_forwarder_0'
-        
+            salt = b"pop3_forwarder_0"
+
         # Derive a proper Fernet key from the provided key
         kdf = PBKDF2HMAC(
             algorithm=hashes.SHA256(),
@@ -96,20 +106,20 @@ class CredentialEncryption:
             salt=salt,
             iterations=100000,
         )
-        key_bytes = key.encode('utf-8')
+        key_bytes = key.encode("utf-8")
         derived_key = base64.urlsafe_b64encode(kdf.derive(key_bytes))
         self.fernet = Fernet(derived_key)
-    
+
     def encrypt(self, plain_text: str) -> str:
         """Encrypt a string and return base64-encoded ciphertext"""
-        encrypted = self.fernet.encrypt(plain_text.encode('utf-8'))
-        return base64.b64encode(encrypted).decode('utf-8')
-    
+        encrypted = self.fernet.encrypt(plain_text.encode("utf-8"))
+        return base64.b64encode(encrypted).decode("utf-8")
+
     def decrypt(self, encrypted_text: str) -> str:
         """Decrypt a base64-encoded ciphertext"""
-        encrypted_bytes = base64.b64decode(encrypted_text.encode('utf-8'))
+        encrypted_bytes = base64.b64decode(encrypted_text.encode("utf-8"))
         decrypted = self.fernet.decrypt(encrypted_bytes)
-        return decrypted.decode('utf-8')
+        return decrypted.decode("utf-8")
 
 
 # Global encryption instance