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.

templates/other.html

@@ -51,6 +51,18 @@
         opacity: 0.6;
         cursor: default;
     }
+    .other-no-paths-config {
+        margin: 4px 0 0;
+        padding: 12px 16px;
+        max-width: 520px;
+        overflow-x: auto;
+        text-align: left;
+        font-size: 12px;
+        line-height: 1.5;
+        border-radius: 6px;
+        background: rgba(127, 127, 127, 0.15);
+        border: 1px solid rgba(127, 127, 127, 0.25);
+    }
 </style>
 {% endblock %}
 
@@ -109,6 +121,28 @@
         </button>
         <p class="other-disabled-hint">{{ t('other.disabled.hint') }}</p>
     </div>
+    {% elif other_no_paths %}
+    <div class="other-disabled">
+        <i class="fas fa-folder-open"></i>
+        <h2>{{ t('other.noPaths.title') }}</h2>
+        {% if standalone_mode %}
+        <p>{{ t('other.noPaths.descriptionStandalone') }}</p>
+        <pre class="other-no-paths-config"><code>"folder_paths": {
+  "vae": ["/path/to/vae"],
+  "upscale_models": ["/path/to/upscale_models"],
+  "text_encoders": ["/path/to/text_encoders"],
+  "clip_vision": ["/path/to/clip_vision"],
+  "controlnet": ["/path/to/controlnet"]
+}</code></pre>
+        <p class="other-disabled-hint">{{ t('other.noPaths.hintStandalone') }}</p>
+        {% else %}
+        <p>{{ t('other.noPaths.descriptionComfyUI') }}</p>
+        <p class="other-disabled-hint">{{ t('other.noPaths.hintComfyUI') }}</p>
+        {% endif %}
+        <button id="openOtherModelsSettingsBtn" type="button">
+            <i class="fas fa-cog"></i> {{ t('other.noPaths.openSettings') }}
+        </button>
+    </div>
     {% else %}
     <div class="sticky-topbar">
     {% include 'components/controls.html' %}
@@ -129,7 +163,7 @@
 {% endblock %}
 
 {% block main_script %}
-{% if other_disabled %}
+{% if other_disabled or other_no_paths %}
 <script type="module" src="/loras_static/js/other_disabled.js?v={{ version }}"></script>
 {% else %}
 <script type="module" src="/loras_static/js/other.js?v={{ version }}"></script>