feat: file upload retry, secure file tokens, UI polish

- Add HMAC-based file token auth for secure AI model file access
- Add file upload retry with exponential backoff (max 3 retries)
- File endpoint now requires session auth or signed token
- Support assistant role messages in chat input
- Optimistic UI for attachments on message send
- Verify topic ownership before allowing messages
- Switch web scraping to Firecrawl API
- Agent profile page layout fixes (proper flex overflow)
- Add quick switcher (Ctrl+K) to sidenav
- Clean up longcat.ts and stale comments

server/utils/providers/closedrouter.ts

@@ -14,7 +14,11 @@ export default {
         }
 
         return Ok({
-            gateway: createOpenAI({ name: 'ClosedRouter', apiKey, baseURL }),
+            gateway: createOpenAI({
+                name: 'ClosedRouter',
+                apiKey,
+                baseURL
+            }),
             streamTransformer: undefined,
             textTransformer: undefined,
         });