feat(cliproxy): add version management UI with install/restart controls

Implements comprehensive version management for CLIProxyAPI Plus:

Backend APIs:
- GET /versions: fetch available versions from GitHub releases
- POST /install: install specific version with force flag for unstable
- POST /restart: restart proxy without version change

Frontend:
- 4-button layout: Restart, Update/Downgrade, Stop, Settings gear
- Collapsible version picker with dropdown + manual input
- Confirmation dialog for unstable versions (>6.6.80)
- Progressive disclosure (version picker hidden by default)

Ref: plans/260105-1250-cliproxy-version-management/

ui/src/hooks/use-cliproxy.ts

@@ -304,3 +304,59 @@ export function useCliproxyUpdateCheck() {
     refetchOnWindowFocus: false, // Don't refresh on window focus (save API calls)
   });
 }
+
+// ==================== Version Management ====================
+
+export function useCliproxyVersions() {
+  return useQuery({
+    queryKey: ['cliproxy-versions'],
+    queryFn: () => api.cliproxy.versions(),
+    staleTime: 60 * 60 * 1000, // 1 hour (matches backend cache)
+    refetchOnWindowFocus: false,
+  });
+}
+
+export function useInstallVersion() {
+  const queryClient = useQueryClient();
+
+  return useMutation({
+    mutationFn: ({ version, force }: { version: string; force?: boolean }) =>
+      api.cliproxy.install(version, force),
+    onSuccess: (data) => {
+      if (data.requiresConfirmation) {
+        // Don't show toast - let caller handle confirmation dialog
+        return;
+      }
+      queryClient.invalidateQueries({ queryKey: ['cliproxy-versions'] });
+      queryClient.invalidateQueries({ queryKey: ['cliproxy-update-check'] });
+      queryClient.invalidateQueries({ queryKey: ['proxy-status'] });
+      if (data.success) {
+        toast.success(data.message || `Installed v${data.version}`);
+      } else {
+        toast.error(data.error || 'Installation failed');
+      }
+    },
+    onError: (error: Error) => {
+      toast.error(error.message);
+    },
+  });
+}
+
+export function useRestartProxy() {
+  const queryClient = useQueryClient();
+
+  return useMutation({
+    mutationFn: () => api.cliproxy.restart(),
+    onSuccess: (data) => {
+      queryClient.invalidateQueries({ queryKey: ['proxy-status'] });
+      if (data.success) {
+        toast.success(`Proxy restarted on port ${data.port}`);
+      } else {
+        toast.error(data.error || 'Restart failed');
+      }
+    },
+    onError: (error: Error) => {
+      toast.error(error.message);
+    },
+  });
+}