fix(providers): add missing providerStrategies state + restore notify store

* page.js referenced setProviderStrategies (line 166) and
  providerStrategies (line 597) but never declared the
  useState — providers page threw ReferenceError on mount.
* The destructure of useNotificationStore() was also dropped
  by the merge of origin/master; 5 sites in the file called
  notify.error/.success/.warning.
* Both were present before the merge (commits de9e00c6 +
  upstream master versions). The statusFilter commit
  (d1d4e0f0) was the last state-block edit and survived,
  but adjacent state lines were lost during the conflict
  resolution.

src/app/(dashboard)/dashboard/providers/page.js

@@ -107,6 +107,7 @@ export default function ProvidersPage() {
   const [testingMode, setTestingMode] = useState(null);
   const [testResults, setTestResults] = useState(null);
   const [statusFilter, setStatusFilter] = useState("all");
+  const [providerStrategies, setProviderStrategies] = useState({});
   const notify = useNotificationStore();
   const searchQuery = useHeaderSearchStore((s) => s.query);
   const registerSearch = useHeaderSearchStore((s) => s.register);