feat(other-models): announce the feature only when folders are available

Other Models management is opt-in and its folders come from
folder_paths.get_folder_paths(). In plugin mode ComfyUI registers vae,
upscale_models, text_encoders, clip_vision and controlnet out of the box, so
enabling the feature works immediately. Standalone only knows the keys present
in settings.json.folder_paths, and that file is edited by hand - there is no UI
for those keys - so a standalone user who followed the announcement banner
reached "Enable Other Models" and then an empty page.

Gate the announcement on the capability instead of on how the process was
started:

- Config.get_other_models_availability() probes every canonical other key
  (legacy clip collapses into text_encoders where the host exposes
  map_legacy) and reports which sub_types resolve to a folder that exists on
  disk. It deliberately ignores enable_other_models: the question is "could
  this work here at all?". An empty folder counts, because CivitAI downloads
  can target it.
- /api/lm/settings exposes it as the derived, non-persisted
  other_models_paths_available flag; a probe failure yields null and the
  banner fails open.
- BannerService only registers the announcement when the flag is not false.
  `=== false` (not falsy) keeps a cached/older payload working, and nothing is
  written to dismissed_banners, so the banner can return once folders exist.
- The Other page grows an "enabled but nothing to scan" empty state driven by
  config.other_roots, showing the settings.json snippet for standalone and a
  pointer to ComfyUI model paths otherwise, plus an Open Settings action. It
  also covers the corner where only a non-default sub_type has a folder.

Translate the six other.noPaths.* keys into all nine locales and record the
new "folder key" / "on disk" terminology in the i18n guidelines.

Backend tests and pytest tests/i18n could not run in this environment (no
pytest/platformdirs); the probe was exercised against a stubbed folder_paths.
Frontend: 120 files / 1101 JS tests passed.

py/routes/other_routes.py

@@ -1,4 +1,5 @@
 import logging
+import os
 from typing import Any, Dict, List
 from aiohttp import web
 
@@ -75,7 +76,18 @@ class OtherRoutes(BaseModelRoutes):
         return self._page_context_for_other
 
     def _page_context_for_other(self, request: web.Request) -> Dict[str, Any]:
-        return {"other_disabled": not self._settings.is_other_models_enabled()}
+        if not self._settings.is_other_models_enabled():
+            return {"other_disabled": True, "other_no_paths": False}
+
+        # Enabled but nothing to scan: folder paths for the managed sub_types
+        # resolved to no existing folder. Render an actionable empty state
+        # instead of an apparently broken empty grid.
+        standalone_mode = os.environ.get("LORA_MANAGER_STANDALONE", "0") == "1"
+        return {
+            "other_disabled": False,
+            "other_no_paths": not bool(config.other_roots),
+            "standalone_mode": standalone_mode,
+        }
 
     def _get_expected_model_types(self) -> str:
         """Get expected model types string for error messages"""