feat: integrate Convex API and add N5 proxy functionality

- Added Convex client setup in a new module for handling Convex API interactions.
- Implemented N5Proxy to handle requests for the /n5/:slug route, querying Convex for application links.
- Updated app context to include Convex client and API.
- Adjusted routing to support new Convex API endpoints.
- Enhanced error handling for missing applications in the N5 proxy.

src/app.ts

@@ -7,7 +7,7 @@ import { BailianProvider } from '@kevisual/ai';
 import * as schema from './db/schema.ts';
 import { config } from './modules/config.ts'
 import { db } from './modules/db.ts'
-
+import { convexClient, convexApi } from './modules/convex.ts'
 export const router = useContextKey('router', () => new SimpleRouter());
 export const runtime = useContextKey('runtime', () => {
   return {
@@ -44,3 +44,6 @@ export const ai = useContextKey('ai', () => {
 
 export { schema };
 
+
+export const convex = useContextKey('convex', () => convexClient);
+export { convexApi };