Enhance backend idle management and diagnostics in SwarmUI

- Updated the `wait_backend_idle` function to handle disabled backends, introducing a new failure condition and diagnostics collection for better error handling.
- Refactored the `install_swarm_comfy` script to include a new `configure_comfy_backend` function, streamlining backend configuration and enabling better management of backend states.
- Added tests to validate the new functionality for handling disabled backends and ensuring robust diagnostics, improving overall backend management.

src/gpu_rent/ready.py

@@ -207,21 +207,25 @@ def wait_backend_idle(
     timeout: float = 2400.0,
     poll_every: float = 15.0,
     errored_fail_sec: float = 120.0,
+    disabled_fail_sec: float = 90.0,
 ) -> None:
     """Block until SwarmUI backends are ready (status=running, no queue).
 
     Note: SwarmUI ``idle`` means suspended backends (cannot generate).
-    Ready-to-use is ``running``. Sustained ``errored`` fail-fasts (won't self-heal).
+    Ready-to-use is ``running``. Sustained ``errored`` / ``disabled`` fail-fasts.
     """
     deadline = time.time() + timeout
     log("жду ready backend (running)…")
     last = ""
     errored_since: float | None = None
+    disabled_since: float | None = None
     pretty = {
         "BUSY backend=loading (Comfy стартует)": "… Comfy стартует",
         "BUSY backend=some_loading (Comfy стартует)": "… Comfy стартует (часть бэкендов)",
         "BUSY backend=empty (нужен first-install Comfy)": "… backend пуст — нужен install",
         "BUSY backend=errored": "… backend errored — смотри journalctl -u swarmui",
+        "BUSY backend=disabled": "… backend disabled (пустой StartScript?)",
+        "BUSY backend=all_disabled": "… все backends disabled",
         "READY backend=running": "backend ready (running)",
         "READY backend=idle (backends present, suspended)": "backend ready (idle/suspended)",
     }
@@ -256,6 +260,19 @@ def wait_backend_idle(
                 )
         else:
             errored_since = None
+        if "BUSY backend=disabled" in line or "BUSY backend=all_disabled" in line:
+            now = time.time()
+            if disabled_since is None:
+                disabled_since = now
+            elif now - disabled_since >= disabled_fail_sec:
+                collect_swarm_diagnostics(cfg, host, log)
+                raise CloudError(
+                    f"backend=disabled уже {int(now - disabled_since)} с — "
+                    "обычно пустой StartScript (нужен dlbackend/ComfyUI/main.py). "
+                    "Диагностика выше. Server → Backends → Edit StartScript или re-run up."
+                )
+        else:
+            disabled_since = None
         time.sleep(poll_every)
     collect_swarm_diagnostics(cfg, host, log)
     raise CloudError(