Add analysis status panel to admin page

- GET /api/admin/stats returns total bills, docs fetched, briefs generated
  (full + amendment), and remaining count
- Admin page shows stat cards + progress bar, auto-refreshes every 30s

Authored-By: Jack Levy

frontend/lib/api.ts

@@ -123,8 +123,20 @@ export interface AdminUser {
   created_at: string;
 }
 
+export interface AnalysisStats {
+  total_bills: number;
+  docs_fetched: number;
+  briefs_generated: number;
+  full_briefs: number;
+  amendment_briefs: number;
+  remaining: number;
+}
+
 // Admin
 export const adminAPI = {
+  // Stats
+  getStats: () =>
+    apiClient.get<AnalysisStats>("/api/admin/stats").then((r) => r.data),
   // Users
   listUsers: () =>
     apiClient.get<AdminUser[]>("/api/admin/users").then((r) => r.data),