🐛 fix(api): add Vercel serverless function for Bilibili search suggestions

- Create api/bilibili.ts to handle Bilibili API requests in production
  - Proxy requests to https://s.search.bilibili.com/main/suggest
  - Add proper headers (User-Agent, Referer) to avoid blocking
  - Set CORS headers and cache control (60s)
  - Handle errors gracefully with fallback response
- Update src/utils/suggestions.ts to detect environment
  - Use /bilibili (Vite proxy) in development
  - Use /api/bilibili (Vercel Function) in production
  - Check import.meta.env.DEV to determine environment

This fixes the 404 error in production where Vite proxy is not available.

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

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

src/utils/suggestions.ts

@@ -22,9 +22,13 @@ export const fetchSuggestions = (engine: string, query: string): Promise<string[
       return;
     }
 
-    // Bilibili uses fetch (via Vite proxy)
+    // Bilibili uses fetch (via Vite proxy in dev, Vercel Function in production)
     if (engine === 'Bilibili') {
-      const url = `/bilibili?term=${encodeURIComponent(query)}`;
+      // In production (Vercel), use /api/bilibili; in development, use /bilibili (Vite proxy)
+      const isDev = import.meta.env.DEV;
+      const url = isDev
+        ? `/bilibili?term=${encodeURIComponent(query)}`
+        : `/api/bilibili?term=${encodeURIComponent(query)}`;
 
       fetch(url)
         .then(response => response.json())