Implement headless ComfyUI installation and improve backend status handling

- Added a new function to ensure headless installation of ComfyUI when backends are empty, enhancing the setup process for SwarmUI.
- Updated documentation to clarify the installation flow and backend readiness checks, ensuring users understand the requirements for a successful setup.
- Enhanced backend status checks to differentiate between 'empty' and 'idle' states, improving error handling and user feedback during provisioning.
- Adjusted logging messages to provide clearer insights into the installation and backend status processes.

src/gpu_rent/provision.py

@@ -92,6 +92,20 @@ def tune_swarm_perf(cfg: Config, host: str, log: Log) -> bool:
     return "RESTART_SWARMUI=1" in out
 
 
+def ensure_swarm_comfy_installed(cfg: Config, host: str, log: Log) -> None:
+    """Headless SwarmUI InstallConfirmWS (ComfyUI) when backends are still empty."""
+    log("SwarmUI first-install: ComfyUI backend (если ещё empty)…")
+    run_python(
+        cfg,
+        host,
+        _pkg_text("install_swarm_comfy.py"),
+        remote_path="/tmp/gpu-rent-install_swarm_comfy.py",
+        # Cold: git clone Comfy + pip torch — often 15–40 min.
+        timeout=3900,
+        log=log,
+    )
+
+
 def seed_extensions(cfg: Config, host: str, log: Log, *, update: bool = True) -> bool:
     from gpu_rent.llm_runtime import normalize_runtime