feat(dashboard): add notification bell with unread count polling

- Add unreadCount state and polling interval (30s) to DashboardDesignPreview
- Fetch from GET /api/me/notifications/unread-count with auth
- Display orange dot badge on bell when unreadCount > 0
- Uses existing bell icon in header; integrates with notifications page

Implements PRD item: Notification bell on dashboard

src/components/admin/DashboardDesignPreview.tsx

@@ -1041,6 +1041,32 @@ export default function DashboardDesignPreview(props: {
 }) {
   const [isVerified, setIsVerified] = createSignal(false);
   const [verificationPending, setVerificationPending] = createSignal(false);
+  const [unreadCount, setUnreadCount] = createSignal(0);
+
+  // Fetch unread notification count
+  const fetchUnreadCount = async () => {
+    try {
+      const token = getToken();
+      if (!token) return;
+      const res = await fetch('/api/me/notifications/unread-count', {
+        headers: { Authorization: `Bearer ${token}` },
+        credentials: 'include',
+      });
+      if (res.ok) {
+        const data = await res.json();
+        setUnreadCount(data.unread_count || 0);
+      }
+    } catch (e) {
+      console.error('Failed to fetch unread count:', e);
+    }
+  };
+
+  // Start polling on mount
+  onMount(() => {
+    fetchUnreadCount();
+    const interval = setInterval(fetchUnreadCount, 30000);
+    return () => clearInterval(interval);
+  });
 
   const isProfessionalRoleKey = (roleKey: string) => {
     const role = normalizeRoleKey(roleKey);
@@ -6657,7 +6683,12 @@ export default function DashboardDesignPreview(props: {
               </div>
             </div>
             <div style="display:flex;align-items:center;gap:8px">
-              <button type="button" style="width:34px;height:34px;border-radius:8px;border:1px solid #E5E7EB;background:white;display:flex;align-items:center;justify-content:center;cursor:pointer;color:#6B7280"><Bell size={16} /></button>
+               <button type="button" style="width:34px;height:34px;border-radius:8px;border:1px solid #E5E7EB;background:white;display:flex;align-items:center;justify-content:center;cursor:pointer;color:#6B7280;position:relative">
+                 <Bell size={16} />
+                 <Show when={unreadCount() > 0}>
+                   <span style="position:absolute;top:-2px;right:-2px;width:8px;height:8px;background:#FF5E13;border-radius:50%;border:1px solid white"></span>
+                 </Show>
+               </button>
               <button type="button" style="width:34px;height:34px;border-radius:8px;border:1px solid #E5E7EB;background:white;display:flex;align-items:center;justify-content:center;cursor:pointer;color:#6B7280"><Settings size={16} /></button>
               <button type="button" style="width:34px;height:34px;border-radius:8px;border:1px solid #E5E7EB;background:white;display:flex;align-items:center;justify-content:center;cursor:pointer;color:#6B7280"><User size={16} /></button>
             </div>