feat(frontend): opt-in Other Models toggles, hidden nav and announcement

- The Other nav entry is hidden while the feature is off
  (nav-item--hidden, toggled client-side after enabling) and now uses the
  fa-shapes icon.
- Shared utils/otherModels.js helpers (enable through the settings API,
  open the settings Library section) are reused by the disabled page, the
  announcement banner and the download modal.
- BannerService registers a one-time dismissible "other-models-announcement"
  banner while the feature is off; SettingsManager drops the banner and
  updates the nav when the master switch flips.
- A disabled download routing answer now surfaces a showActionToast with an
  "Enable Other Models" action.
- Settings UI: master toggle + five sub_type checkboxes whose default-root
  selects are disabled when unchecked; i18n keys added to en.json and synced
  (other locales keep TODO placeholders).

tests/frontend/managers/BannerService.test.js

@@ -27,6 +27,14 @@ vi.mock('../../../static/js/state/index.js', () => ({
     }
 }));
 
+// Mock the shared Other Models helpers (exercised by their own tests)
+vi.mock('../../../static/js/utils/otherModels.js', () => ({
+    enableOtherModels: vi.fn().mockResolvedValue(),
+    openOtherModelsSettings: vi.fn(),
+}));
+
+import { enableOtherModels, openOtherModelsSettings } from '../../../static/js/utils/otherModels.js';
+
 describe('BannerService', () => {
     beforeEach(() => {
         // Clear all mocks
@@ -186,6 +194,91 @@ describe('BannerService', () => {
         });
     });
 
+    describe('Other Models announcement', () => {
+        const OTHER_MODELS_BANNER_ID = 'other-models-announcement';
+
+        const prepareBanner = (dismissed = []) => {
+            storageHelpers.getStorageItem.mockImplementation((key, defaultValue) => {
+                if (key === 'dismissed_banners') {
+                    return dismissed;
+                }
+                return defaultValue;
+            });
+            bannerService.container = document.getElementById('banner-container');
+            bannerService.initialized = true;
+            bannerService.prepareOtherModelsBanner();
+        };
+
+        const bannerElement = () =>
+            document.querySelector(`[data-banner-id="${OTHER_MODELS_BANNER_ID}"]`);
+
+        beforeEach(() => {
+            state.global.settings.enable_other_models = false;
+        });
+
+        it('announces the feature while it is switched off', () => {
+            prepareBanner();
+
+            const element = bannerElement();
+            expect(element).not.toBeNull();
+            expect(element.querySelector('.banner-title').textContent)
+                .toContain('Other Models Management is available');
+        });
+
+        it('stays silent once the feature is enabled', () => {
+            state.global.settings.enable_other_models = true;
+
+            prepareBanner();
+
+            expect(bannerElement()).toBeNull();
+        });
+
+        it('stays silent when it was dismissed before', () => {
+            prepareBanner([OTHER_MODELS_BANNER_ID]);
+
+            expect(bannerElement()).toBeNull();
+        });
+
+        it('enables the feature from the primary action', () => {
+            prepareBanner();
+
+            const button = bannerElement().querySelector(
+                '.banner-action[data-action="enable-other-models"]'
+            );
+            expect(button).not.toBeNull();
+
+            button.dispatchEvent(new MouseEvent('click', { bubbles: true }));
+
+            expect(enableOtherModels).toHaveBeenCalledTimes(1);
+        });
+
+        it('opens the settings section from the secondary action', () => {
+            prepareBanner();
+
+            const button = bannerElement().querySelector(
+                '.banner-action[data-action="open-other-models-settings"]'
+            );
+            expect(button).not.toBeNull();
+
+            button.dispatchEvent(new MouseEvent('click', { bubbles: true }));
+
+            expect(openOtherModelsSettings).toHaveBeenCalledTimes(1);
+        });
+
+        it('can drop the announcement without dismissing it', () => {
+            prepareBanner();
+            expect(bannerService.banners.has(OTHER_MODELS_BANNER_ID)).toBe(true);
+
+            bannerService.removeOtherModelsAnnouncement();
+
+            expect(bannerService.banners.has(OTHER_MODELS_BANNER_ID)).toBe(false);
+            expect(storageHelpers.setStorageItem).not.toHaveBeenCalledWith(
+                'dismissed_banners',
+                expect.arrayContaining([OTHER_MODELS_BANNER_ID])
+            );
+        });
+    });
+
     describe('Banner Dismissal', () => {
         it('should add banner to dismissed_banners array when dismissed', () => {
             storageHelpers.getStorageItem.mockImplementation((key, defaultValue) => {