feat(05-01): add Phase 5 cloud fixtures to conftest.py

Appends 4 new fixtures to backend/tests/conftest.py:
- mock_google_drive_creds: Google OAuth credential dict (access/refresh token, expiry)
- mock_onedrive_creds: OneDrive MSAL credential dict
- mock_webdav_client: MagicMock with upload_to/download_from/list/check methods
- cloud_connection_factory: async factory that creates CloudConnection ORM rows

All existing fixtures and tests unaffected; pytest collection errors = 0.

backend/tests/conftest.py

@@ -302,3 +302,107 @@ def mock_minio_stat(monkeypatch):
     except ImportError:
         pass  # storage module not yet available — patch is best-effort
     yield mock
+
+
+# ── Phase 5 cloud storage fixtures ───────────────────────────────────────────
+
+
+@pytest.fixture
+def mock_google_drive_creds():
+    """Return a fake Google Drive OAuth credential dict for unit tests.
+
+    Shape mirrors what google-auth-oauthlib stores in credentials.to_json().
+    Expiry is far in the future so tests never hit a token-refresh branch.
+    """
+    return {
+        "access_token": "ya29.test_access",
+        "refresh_token": "1//test_refresh",
+        "expiry": "2099-12-31T23:59:59",
+        "token_uri": "https://oauth2.googleapis.com/token",
+        "client_id": "test_client_id",
+        "client_secret": "test_client_secret",
+    }
+
+
+@pytest.fixture
+def mock_onedrive_creds():
+    """Return a fake OneDrive MSAL credential dict for unit tests.
+
+    Shape mirrors what msal.PublicClientApplication.acquire_token_by_auth_code_flow
+    returns (simplified subset required by cloud_utils).
+    """
+    return {
+        "access_token": "test_ms_access",
+        "refresh_token": "test_ms_refresh",
+        "expires_at": "2099-12-31T23:59:59",
+    }
+
+
+@pytest.fixture
+def mock_webdav_client():
+    """Return a MagicMock simulating a webdavclient3 Client instance.
+
+    All four methods the DocuVault cloud layer calls are pre-wired to return None
+    so tests can assert call counts without making real network connections.
+    """
+    from unittest.mock import MagicMock
+
+    client = MagicMock()
+    client.upload_to = MagicMock(return_value=None)
+    client.download_from = MagicMock(return_value=None)
+    client.list = MagicMock(return_value=None)
+    client.check = MagicMock(return_value=None)
+    return client
+
+
+@pytest_asyncio.fixture
+async def cloud_connection_factory(db_session: AsyncSession):
+    """Factory fixture that creates CloudConnection ORM rows in the test db_session.
+
+    Usage::
+
+        async def test_something(cloud_connection_factory, auth_user):
+            conn = await cloud_connection_factory(
+                db_session, auth_user["user"].id, provider="google_drive"
+            )
+            assert conn.status == "ACTIVE"
+
+    Parameters
+    ----------
+    session : AsyncSession
+        The async SQLAlchemy session to use (typically db_session).
+    user_id : uuid.UUID | str
+        Owner of the cloud connection.
+    provider : str
+        Provider slug, e.g. "google_drive", "onedrive", "webdav".
+    status : str
+        Connection status string, default "ACTIVE".
+    display_name : str | None
+        Human-readable label; defaults to "<provider> account".
+    credentials_enc : str
+        Encrypted credential blob (use a placeholder in unit tests).
+    """
+    import uuid as _uuid
+    from db.models import CloudConnection
+
+    async def _factory(
+        session: AsyncSession,
+        user_id,
+        provider: str = "google_drive",
+        status: str = "ACTIVE",
+        display_name: str | None = None,
+        credentials_enc: str = "fake_encrypted_creds",
+    ) -> CloudConnection:
+        conn = CloudConnection(
+            id=_uuid.uuid4(),
+            user_id=user_id if isinstance(user_id, _uuid.UUID) else _uuid.UUID(str(user_id)),
+            provider=provider,
+            display_name=display_name or f"{provider} account",
+            credentials_enc=credentials_enc,
+            status=status,
+        )
+        session.add(conn)
+        await session.flush()
+        return conn
+
+    return _factory