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>

frontend/src/lib/api.ts

@@ -544,6 +544,8 @@ export const settingsApi = {
 export interface VehicleRequest {
   id: number;
   user_id: number;
+  user_email?: string;  // 관리자용
+  user_name?: string;   // 관리자용
   maker_code?: string;
   maker_name?: string;
   model_code?: string;

frontend/src/lib/i18n.ts

@@ -2994,6 +2994,12 @@ const CAR_TRANSLATIONS: Record<string, Record<string, string>> = {
   '듀얼': { ko: '듀얼', en: 'Dual', mn: 'Dual', ru: 'Дуал' },
   '싱글': { ko: '싱글', en: 'Single', mn: 'Single', ru: 'Сингл' },
   '트윈': { ko: '트윈', en: 'Twin', mn: 'Twin', ru: 'Твин' },
+  // Fuel Types (추가분)
+  '경유': { ko: '경유', en: 'Diesel', mn: 'Дизель', ru: 'Дизель' },
+  '휘발유': { ko: '휘발유', en: 'Gasoline', mn: 'Бензин', ru: 'Бензин' },
+  // Transmission Types (추가분)
+  '오토': { ko: '오토', en: 'Automatic', mn: 'Автомат', ru: 'Автомат' },
+  '수동': { ko: '수동', en: 'Manual', mn: 'Механик', ru: 'Механика' },
 };
 
 // Sorted keys for translation (longest first to avoid partial matches)