139:def refresh_access_token(client: dict, refresh_token: str) -> dict:
140-    data = {
141-        "client_id": client["client_id"],
142-        "client_secret": client["client_secret"],
143-        "refresh_token": refresh_token,
144-        "grant_type": "refresh_token",
145-    }
146-    resp = requests.post(GOOGLE_TOKEN_URL, data=data, timeout=20)
147-    if resp.status_code != 200:
--
173:class GmailClient:
174-    """Authenticated Gmail client for one account (API or XOAUTH2 SMTP)."""
175-
176-    def __init__(self, account_email: str, access_token: str, refresh_token: str,
177-                 client_config: dict, sending_method: str = "api", token_expiry=None):
178-        self.account_email = account_email
179-        self.client_config = client_config
180-        self.method = sending_method if sending_method in ("api", "smtp") else "api"
181-        creds = gcred.Credentials(
--
193:    def _ensure_valid(self):
194-        request = google.auth.transport.requests.Request()
195-        if not self._creds.valid:
196-            self._creds.refresh(request)
197-        return self._creds.token
198-
199:    def _api(self):
200-        if self._service is None:
201-            self._ensure_valid()
202-            self._service = build("gmail", "v1", credentials=self._creds, cache_discovery=False)
203-        else:
204-            self._ensure_valid()
205-        return self._service
206-
207-    # -- API send ------------------------------------------------------------
--
249:def build_gmail_client_from_account(account, oauth_token, client_config=None) -> GmailClient:
250-    """Build a GmailClient from DB rows (sync session context - worker uses sync ORM)."""
251-    cfg = client_config or resolve_client_config_for_account(account)
252-    return GmailClient(
253-        account_email=account.email,
254-        access_token=oauth_token.access_token,       # decrypted
255-        refresh_token=oauth_token.refresh_token,     # decrypted
256-        client_config=cfg,
257-        sending_method=account.sending_method,