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/Sidenav/NavAgent.vue

@@ -1,7 +1,9 @@
 <script setup lang="ts">
 import RowVirtualizerFixed from '~/components/RowVirtualizerFixed.vue';
 import { useFloating, offset, flip, shift, autoUpdate, hide } from '@floating-ui/vue';
+import { DialogType } from '~/composables/useDialog';
 
+const { openDialog } = useDialog();
 const dropdownOpen = ref(false);
 const dropdownTrigger = ref<HTMLElement | null>(null);
 const dropdownContent = ref(null);
@@ -151,6 +153,17 @@ onMounted(() => {
         <SidenavItem :to="`/agent/${agentId}/profile`" name="Agent Info" icon="i-mynaui-info-square"
             :active="route.path.endsWith('/profile')" />
 
+        <SidenavItem @click="openDialog(DialogType.QuickSwitcher)" name="Search" icon="i-mynaui-search">
+            <div class="flex items-center gap-1">
+                <span class="flex bg-[var(--bg-container)] px-1 rounded border border-[var(--color-border)]">
+                    <kbd class="font-mono text-[10px] case-capital">ctrl</kbd>
+                </span>
+                <span class="flex bg-[var(--bg-container)] px-1 rounded border border-[var(--color-border)]">
+                    <kbd class="font-mono text-[10px] case-capital">k</kbd>
+                </span>
+            </div>
+        </SidenavItem>
+
         <!-- Topics Section -->
         <button @click="topicsOpen = !topicsOpen"
             class="flex items-center justify-between gap-2 px-2 py-2 rounded-lg bg-transparent @hover:bg-[var(--color-hover)] focus-visible:bg-[var(--color-hover)] transition-colors w-full text-left">