fix: merge main, resolve conflicts, address review feedback

- Resolve merge conflicts in app/api/onedrive.py and tests/test_api_google_drive_final.py
- Fix legacy Dict[str, str] type hints in update_env_file functions to use dict[str, str]
- Add admin-only access (_require_admin dependency) to save-settings endpoints
  in google_drive.py, onedrive.py, and dropbox.py
- Fix in_memory_only response field to reflect actual env_write_success status
- Update tests to override _require_admin dependency for save-settings endpoint tests

tests/test_api_google_drive_final.py

@@ -154,6 +154,15 @@ class TestGetTokenInfoCredentialsBranches:
 class TestSaveGoogleDriveSettingsFalsyFields:
     """Cover branches 395->397, 449->451, 468->470 in save_google_drive_settings."""
 
+    @pytest.fixture(autouse=True)
+    def _admin_override(self):
+        from app.api.google_drive import _require_admin
+        from app.main import app as fastapi_app
+
+        fastapi_app.dependency_overrides[_require_admin] = lambda: {"is_admin": True}
+        yield
+        fastapi_app.dependency_overrides.pop(_require_admin, None)
+
     @patch("app.api.google_drive.settings")
     @patch("os.path.exists", return_value=False)
     @pytest.mark.asyncio
@@ -173,6 +182,7 @@ class TestSaveGoogleDriveSettingsFalsyFields:
             with patch("app.api.google_drive.notify_settings_updated"):
                 result = await save_google_drive_settings(
                     request=mock_request,
+                    _admin={"is_admin": True},
                     refresh_token="",  # falsy → branches 395->397 and 449->451
                     client_id="cid",
                     client_secret=None,