🔍 feat(ratio-sync): add fuzzy model search & enhance empty-state UX

Summary
1. Add model name search box
   • Introduce Semi UI `Input` with `IconSearch` prefix next to the “Apply Sync” button.
   • Support case-insensitive fuzzy matching of model names.
   • Real-time filtering, pagination and bulk-select logic now work on filtered data.

2. Improve empty state handling
   • Add `hasSynced` flag to distinguish “not synced yet” from “synced with no differences”.
   • Display messages:
     – “Please select sync channels” when no sync has been performed.
     – “No differences found” when a sync completed with zero discrepancies.
     – “No matching model found” when search yields no results.

3. UI tweaks
   • Replace lucide-react `Search` icon with Semi UI `IconSearch` for visual consistency.
   • Keep responsive width and clearable input for better usability.

Why
These changes allow admins to quickly locate specific models and provide accurate feedback on the sync status, greatly improving the usability of the Upstream Ratio Sync page.

web/src/i18n/locales/en.json

@@ -1687,5 +1687,6 @@
   "缓存倍率": "Cache ratio",
   "暂无差异化倍率显示": "No differential ratio display",
   "请先选择同步渠道": "Please select the synchronization channel first",
-  "与本地相同": "Same as local"
+  "与本地相同": "Same as local",
+  "未找到匹配的模型": "No matching model found"
 }