Add debug logging to auto-login twofa step

Prints twofa response status, Location header, and body so we can see
exactly what Zerodha returns after TOTP submission.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/app/services/auto_login_service.py

@@ -221,6 +221,12 @@ def _perform_zerodha_login(
         timeout=15,
         allow_redirects=False,
     )
+    print(
+        f"[AUTO-LOGIN-DEBUG] twofa status={twofa_resp.status_code} "
+        f"location={twofa_resp.headers.get('Location', 'NONE')} "
+        f"body={twofa_resp.text[:300]}",
+        flush=True,
+    )
 
     # Step 4: Follow redirects manually to intercept request_token
     request_token = None