Adopt React Query and live updates across all UI pages

Replace custom useApi/useAgents hooks with @tanstack/react-query.
Add LiveUpdatesProvider for WebSocket-driven cache invalidation.
Add queryKeys module for centralized cache key management. Rework
all pages and dialogs to use React Query mutations and queries.
Improve CompanyContext with query-based data fetching.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

ui/vite.config.ts

@@ -13,7 +13,10 @@ export default defineConfig({
   server: {
     port: 5173,
     proxy: {
-      "/api": "http://localhost:3100",
+      "/api": {
+        target: "http://localhost:3100",
+        ws: true,
+      },
     },
   },
 });