feat(tunnels): switch to temporary Cloudflare tunnels

Replace persistent Cloudflare tunnels (API-based) with temporary tunnels using
'cloudflared tunnel --url'. This removes the need for Cloudflare API tokens,
DNS records, and persistent tunnel management.

Changes:
- Install cloudflared binary in API Dockerfile
- Add start_cloudflared_tunnel() and stop_cloudflared_tunnel() to docker.py
- Update instance start/stop/restart/delete to use temporary tunnels
- Store tunnel PID in tunnel_id field, temporary URL in url/public_url
- Remove Cloudflare API service (cloudflare_tunnel.py)
- Remove cloudflared container from docker-compose
- Remove Cloudflare env vars (CLOUDFLARE_API_TOKEN, ZONE_ID, etc.)
- Remove Cloudflare configuration from config.py
- Remove Cloudflare startup check from main.py
- Remove /health/cloudflare endpoint

apps/api/src/services/docker.py

@@ -232,3 +232,79 @@ def find_free_port(start: int = 10000, end: int = 20000) -> int:
                 return port
 
     raise RuntimeError(f"No free port found in range {start}-{end}")
+
+
+import subprocess
+import time
+import re
+
+
+def start_cloudflared_tunnel(
+    container_name: str, port: int, timeout: int = 30
+) -> dict[str, str]:
+    """Start a temporary Cloudflare tunnel for a container.
+
+    Uses 'cloudflared tunnel --url' to create a temporary tunnel
+    with a random trycloudflare.com URL.
+
+    Args:
+        container_name: Name of the Docker container to tunnel to
+        port: Port number the container listens on
+        timeout: Maximum seconds to wait for tunnel URL
+
+    Returns:
+        Dict with 'url' (the public tunnel URL) and 'pid' (process ID)
+    """
+    import subprocess
+    import time
+    import re
+
+    # Run cloudflared in background, capture output
+    proc = subprocess.Popen(
+        ["cloudflared", "tunnel", "--url", f"http://{container_name}:{port}"],
+        stdout=subprocess.PIPE,
+        stderr=subprocess.STDOUT,
+        text=True,
+    )
+
+    # Wait for the URL to appear in output
+    url_pattern = re.compile(r"https://[a-z0-9-]+\.trycloudflare\.com")
+    start_time = time.time()
+    url = None
+
+    while time.time() - start_time < timeout:
+        # Read available output
+        import select
+        readable, _, _ = select.select([proc.stdout], [], [], 1.0)
+        if readable:
+            line = proc.stdout.readline()
+            if line:
+                match = url_pattern.search(line)
+                if match:
+                    url = match.group(0)
+                    break
+
+    if not url:
+        proc.terminate()
+        proc.wait(timeout=5)
+        raise RuntimeError(
+            f"Failed to get tunnel URL within {timeout}s. "
+            f"cloudflared output may contain errors."
+        )
+
+    return {"url": url, "pid": str(proc.pid)}
+
+
+def stop_cloudflared_tunnel(pid: str) -> None:
+    """Stop a cloudflared tunnel process.
+
+    Args:
+        pid: Process ID of the cloudflared tunnel
+    """
+    import os
+    import signal
+
+    try:
+        os.kill(int(pid), signal.SIGTERM)
+    except ProcessLookupError:
+        pass  # Already stopped