fix: Carmodoo session expiry causing all searches to return 0 results

Detect GoLogin redirect response (126 bytes) when session cookies expire,
automatically re-login and retry the search once.

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

backend/app/api/carmodoo.py

@@ -158,6 +158,14 @@ class CarmodooClient:
             print(f"Carmodoo login error: {e}")
             return False
 
+    def _is_login_redirect(self, content: bytes) -> bool:
+        """응답이 로그인 리다이렉트인지 확인"""
+        if len(content) < 200:
+            text = content.decode('utf-8', errors='replace')
+            if 'GoLogin' in text or 'goLogin' in text:
+                return True
+        return False
+
     async def search_cars(
         self,
         maker_code: Optional[str] = None,
@@ -172,7 +180,8 @@ class CarmodooClient:
         transmission: Optional[str] = None,
         complex_code: Optional[str] = None,  # 단지 코드
         page: int = 1,
-        page_size: int = 50
+        page_size: int = 50,
+        _retry: bool = False
     ) -> List[dict]:
         """차량 검색 (POST 방식 AJAX API 호출)"""
 
@@ -270,6 +279,29 @@ class CarmodooClient:
 
                 print(f"[search_cars] Response status: {response.status_code}, content length: {len(response.content)}")
 
+                # 세션 만료 감지 → 재로그인 후 재시도
+                if self._is_login_redirect(response.content):
+                    if not _retry:
+                        print("[search_cars] Session expired (GoLogin detected), re-logging in...")
+                        self.is_logged_in = False
+                        self.cookies = None
+                        login_result = await self.login()
+                        print(f"[search_cars] Re-login result: {login_result}")
+                        if login_result:
+                            return await self.search_cars(
+                                maker_code=maker_code, model_code=model_code,
+                                year_min=year_min, year_max=year_max,
+                                mileage_min=mileage_min, mileage_max=mileage_max,
+                                price_min=price_min, price_max=price_max,
+                                fuel=fuel, transmission=transmission,
+                                complex_code=complex_code,
+                                page=page, page_size=page_size,
+                                _retry=True
+                            )
+                    else:
+                        print("[search_cars] Session expired even after re-login, giving up")
+                    return []
+
                 if response.status_code == 200:
                     html = self._decode_response(response.content)
                     print(f"[search_cars] Decoded HTML length: {len(html)}")