Enhance installation state management and diagnostics for ComfyUI

- Updated the `gpu-rent` logic to ensure the `IsInstalled` flag is accurately set based on the presence of ComfyUI, preventing conflicts during installation.
- Improved the handling of the `/mnt/swarm_data` directory to skip creation if it does not exist, enhancing robustness in provisioning.
- Added tests to validate the new installation state checks and ensure proper diagnostics during the installation process, including scenarios for clearing and setting the `IsInstalled` flag.

tests/test_wait_backend_idle.py

@@ -48,6 +48,9 @@ def test_install_swarm_comfy_script_payload():
     assert "absolute StartScript" in text or "reconfigure errored" in text
     assert "/mnt/swarm_data" in text or "DATA /" in text
     assert 'bstat in ("empty", "disabled", "all_disabled", "unknown")' in text
+    assert "prepare_first_install" in text
+    assert "already installed" in text
+    assert "Open SwarmUI → Server → Backends" not in text
 
 
 def test_wait_backend_idle_fail_fast_on_long_loading(monkeypatch):