feat(sessions): add stop confirmation, health checks, and tunnel recreation

- Add inline confirmation dialog before stopping instances
- Delete instances from state immediately without page reload
- Add health check polling every 30s for running instances
- Show tunnel error badge when tunnel is unreachable
- Add 'Fix Tunnel' button to recreate broken tunnels
- Update API client with health check and tunnel recreation endpoints

apps/web/src/api/sessions.ts

@@ -100,3 +100,25 @@ export async function getUserSessions(): Promise<Session[]> {
   const response = await apiClient.get("/users/me/sessions");
   return response.data.sessions;
 }
+
+export async function checkInstanceHealth(
+  projectId: string,
+  repoId: string,
+  instanceId: string
+): Promise<{ healthy: boolean; status_code: number | null; error?: string }> {
+  const response = await apiClient.get(
+    `/projects/${projectId}/repositories/${repoId}/instances/${instanceId}/health`
+  );
+  return response.data;
+}
+
+export async function recreateInstanceTunnel(
+  projectId: string,
+  repoId: string,
+  instanceId: string
+): Promise<{ status: string; url?: string }> {
+  const response = await apiClient.post(
+    `/projects/${projectId}/repositories/${repoId}/instances/${instanceId}/recreate-tunnel`
+  );
+  return response.data;
+}