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

app/components/Attachment/Display.vue

@@ -10,9 +10,14 @@ const props = defineProps<{
         status?: 'uploading' | 'uploaded' | 'error';
         url: string;
         progress?: number;
+        retryCount?: number;
     };
 }>();
 
+const emit = defineEmits<{
+    retry: [];
+}>();
+
 const isImage = computed(() => props.file.mimeType.startsWith('image/'));
 const isVideo = computed(() => props.file.mimeType.startsWith('video/'));
 const isAudio = computed(() => props.file.mimeType.startsWith('audio/'));
@@ -71,8 +76,20 @@ function openImageViewer() {
             class="absolute inset-0 bg-black/50 rounded-lg flex items-center justify-center">
             <div class="text-center">
                 <span class="i-svg-spinners-90-ring-with-bg text-6 text-white block mb-1"></span>
-                <span class="text-xs text-white">{{ file.progress || 0 }}%</span>
+                <span class="text-xs text-white">
+                    {{ file.retryCount ? `Retry ${file.retryCount}/3` : `${file.progress || 0}%` }}
+                </span>
             </div>
         </div>
+        <div v-else-if="file.status === 'error'"
+            class="absolute inset-0 bg-black/60 rounded-lg flex flex-col items-center justify-center gap-1">
+            <span class="i-mynaui-danger-triangle text-6 text-red-400"></span>
+            <span class="text-xs text-red-300">Upload failed</span>
+            <button @click.stop="emit('retry')"
+                class="mt-1 flex items-center gap-1 px-2 py-0.5 rounded-md bg-white/10 hover:bg-white/20 text-xs text-white transition-colors">
+                <span class="i-mynaui-refresh text-3"></span>
+                Retry
+            </button>
+        </div>
     </div>
 </template>