fix: mobile keyboard handlers killed on SSE reconnect — re-init after cleanup

handleInit() called KeyboardHandler.cleanup() and MobileDetection.cleanup()
on every SSE connect but never re-initialized them, breaking keyboard
scroll-into-view and the /init /clear accessory bar on mobile.

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

src/web/server.ts

@@ -593,12 +593,12 @@ export class WebServer extends EventEmitter {
       done();
     });
 
-    // Serve static files with caching headers for immutable CDN-like assets
+    // Serve static files — versioned assets (?v=X) are immutable, cache aggressively
     await this.app.register(fastifyStatic, {
       root: join(__dirname, 'public'),
       prefix: '/',
-      // Cache static assets for 1 hour (they change on deploy, not during session)
-      maxAge: '1h',
+      maxAge: '1y',
+      immutable: true,
     });
 
     // SSE endpoint for real-time updates