refactor: Remove unused DB translation system

Static dictionary (i18n.ts CAR_TRANSLATIONS) already covers all terms.
DB translations table had only 179 entries used as fallback and was
never actually reached. Simplifies useTranslate hook to static-only.
DB table preserved for safety.

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

frontend/src/lib/useTranslate.ts

@@ -1,74 +1,16 @@
-import { useState, useEffect, useCallback } from 'react';
-import { translationsApi } from './api';
+import { useCallback } from 'react';
 import { useLanguageStore, translateCarName, Language } from './i18n';
 
-// Cache for translations to avoid repeated API calls
-const translationCache: Record<string, Record<string, string>> = {};
-
 export function useTranslate() {
   const { language } = useLanguageStore();
-  const [translations, setTranslations] = useState<Record<string, string>>({});
-  const [loading, setLoading] = useState(false);
 
-  // Get cache key for current language
-  const cacheKey = `trans_${language}`;
-
-  // Load translations from cache on mount
-  useEffect(() => {
-    if (translationCache[cacheKey]) {
-      setTranslations(translationCache[cacheKey]);
-    }
-  }, [cacheKey]);
-
-  // Translate a single text
+  // Translate a single text using static dictionary
   const translate = useCallback((text: string | undefined | null): string => {
     if (!text) return '';
     if (language === 'ko') return text; // Korean is source, no translation needed
 
-    // Try static translations FIRST (for fuel, transmission, car names, etc.)
-    const staticTranslation = translateCarName(text, language as Language);
-    if (staticTranslation !== text) {
-      return staticTranslation;
-    }
-
-    // Then check API cache for other translations
-    const cached = translationCache[cacheKey]?.[text];
-    if (cached) return cached;
-
-    return text; // Fallback to original if no translation found
-  }, [language, cacheKey]);
-
-  // Bulk load translations for multiple texts
-  const loadTranslations = useCallback(async (texts: string[], category?: string) => {
-    if (language === 'ko') return; // No need to translate Korean
-
-    // Filter out already cached texts
-    const uncachedTexts = texts.filter(
-      t => t && !translationCache[cacheKey]?.[t]
-    );
-
-    if (uncachedTexts.length === 0) return;
-
-    setLoading(true);
-    try {
-      // Map language code to API expected format
-      const langCode = language === 'mn' ? 'mn' : language === 'ru' ? 'ru' : 'en';
-
-      const result = await translationsApi.bulkLookup(uncachedTexts, langCode, category);
-
-      // Update cache
-      if (!translationCache[cacheKey]) {
-        translationCache[cacheKey] = {};
-      }
-
-      Object.assign(translationCache[cacheKey], result.translations);
-      setTranslations({ ...translationCache[cacheKey] });
-    } catch (err) {
-      console.error('Failed to load translations:', err);
-    } finally {
-      setLoading(false);
-    }
-  }, [language, cacheKey]);
+    return translateCarName(text, language as Language);
+  }, [language]);
 
   // Translate car object fields
   const translateCar = useCallback((car: {
@@ -89,8 +31,8 @@ export function useTranslate() {
     };
   }, [translate]);
 
-  // Preload translations for a list of cars
-  const preloadCarTranslations = useCallback(async (cars: Array<{
+  // Kept for API compatibility - static translations are synchronous, so this is a no-op
+  const preloadCarTranslations = useCallback(async (_cars: Array<{
     car_name?: string;
     fuel?: string;
     transmission?: string;
@@ -98,37 +40,13 @@ export function useTranslate() {
     maker?: { name: string };
     model?: { name: string };
   }>) => {
-    const textsToTranslate: string[] = [];
-
-    cars.forEach(car => {
-      if (car.car_name) textsToTranslate.push(car.car_name);
-      if (car.fuel) textsToTranslate.push(car.fuel);
-      if (car.transmission) textsToTranslate.push(car.transmission);
-      if (car.color) textsToTranslate.push(car.color);
-      if (car.maker?.name) textsToTranslate.push(car.maker.name);
-      if (car.model?.name) textsToTranslate.push(car.model.name);
-    });
-
-    // Remove duplicates
-    const uniqueTexts = Array.from(new Set(textsToTranslate));
-
-    if (uniqueTexts.length > 0) {
-      await loadTranslations(uniqueTexts);
-    }
-  }, [loadTranslations]);
+    // No-op: static dictionary translations are synchronous
+  }, []);
 
   return {
     translate,
     translateCar,
-    loadTranslations,
     preloadCarTranslations,
-    loading,
+    loading: false,
   };
 }
-
-// Clear translation cache (useful when translations are updated)
-export function clearTranslationCache() {
-  Object.keys(translationCache).forEach(key => {
-    delete translationCache[key];
-  });
-}