Feature: Russian language support & Vehicle Requests improvements

- Add Russian language support (title_ru, subtitle_ru) for hero banners
- Add fuel/transmission translations for Mongolian (경유→Дизель, 오토→Автомат)
- Improve Vehicle Requests admin page:
  - Display real request ID and user email
  - Show detailed request info (maker, grade, year, fuel, mileage)
  - Replace modal search with Cars page integration
- Add "Add to Request" flow in Cars page for vehicle recommendations
- Fix image URL handling in FilmStripSlider and car detail page

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/api/vehicle_requests.py

@@ -143,7 +143,36 @@ def admin_get_all_requests(
         query = query.filter(VehicleRequest.status == status)
 
     requests = query.order_by(VehicleRequest.created_at.desc()).all()
-    return requests
+
+    # User 정보 추가
+    result = []
+    for req in requests:
+        user = db.query(User).filter(User.id == req.user_id).first()
+        req_dict = {
+            "id": req.id,
+            "user_id": req.user_id,
+            "user_email": user.email if user else None,
+            "user_name": user.name if user else None,
+            "maker_code": req.maker_code,
+            "maker_name": req.maker_name,
+            "model_code": req.model_code,
+            "model_name": req.model_name,
+            "grade_code": req.grade_code,
+            "grade_name": req.grade_name,
+            "year_from": req.year_from,
+            "year_to": req.year_to,
+            "mileage_min": req.mileage_min,
+            "mileage_max": req.mileage_max,
+            "fuel": req.fuel,
+            "displacement_min": req.displacement_min,
+            "displacement_max": req.displacement_max,
+            "status": req.status,
+            "admin_reviewed_at": req.admin_reviewed_at,
+            "created_at": req.created_at,
+        }
+        result.append(req_dict)
+
+    return result
 
 
 @router.get("/admin/{request_id}", response_model=VehicleRequestWithVehicles)