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/api/src/services/docker.py

@@ -329,3 +329,57 @@ def stop_cloudflared_tunnel(pid: str) -> None:
         os.kill(int(pid), signal.SIGTERM)
     except ProcessLookupError:
         pass  # Already stopped
+
+
+def recreate_tunnel(
+    container_name: str, port: int, old_pid: str | None = None
+) -> dict[str, str]:
+    """Recreate a temporary Cloudflare tunnel.
+
+    Stops the old tunnel (if pid provided) and starts a new one.
+
+    Args:
+        container_name: Name of the Docker container to tunnel to
+        port: Port number the container listens on
+        old_pid: Optional PID of the old tunnel process to stop
+
+    Returns:
+        Dict with 'url' and 'pid' for the new tunnel
+    """
+    if old_pid:
+        stop_cloudflared_tunnel(old_pid)
+
+    return start_cloudflared_tunnel(container_name, port)
+
+
+def check_tunnel_health(url: str, timeout: int = 10) -> dict[str, any]:
+    """Check if a tunnel URL is healthy.
+
+    Args:
+        url: The tunnel URL to check
+        timeout: Request timeout in seconds
+
+    Returns:
+        Dict with 'healthy' (bool) and 'status_code' (int or None)
+    """
+    import subprocess
+
+    try:
+        result = subprocess.run(
+            ["curl", "-s", "-o", "/dev/null", "-w", "%{http_code}",
+             "--max-time", str(timeout), url],
+            capture_output=True,
+            text=True,
+            timeout=timeout + 5,
+        )
+        status_code = int(result.stdout.strip())
+        return {
+            "healthy": 200 <= status_code < 400,
+            "status_code": status_code,
+        }
+    except (ValueError, subprocess.TimeoutExpired, Exception) as e:
+        return {
+            "healthy": False,
+            "status_code": None,
+            "error": str(e),
+        }