feat(models): add group-by-model option to collapse multiple versions into one card

Adds a 'Group by Model' toggle in Layout Settings. When enabled, only the
latest version (highest civitai.id) of each Civitai model is shown as a
single card — older versions sharing the same modelId are hidden.

Backend dedup runs in BaseModelService.get_paginated_data() before
filtering/pagination, ensuring correct paginated results. The setting
is persisted via the existing settings pipeline and passed as a query
parameter to the listing endpoint.

Includes:
- Backend: dedup logic, route param parsing, settings default
- Frontend: API param, SettingsManager wiring, toggle UI
- i18n: translations for all 10 locales
- Tests: unit test covering dedup on/off and standalone items

static/js/api/baseModelApi.js

@@ -1271,6 +1271,11 @@ export class BaseModelApiClient {
 
         params.append('recursive', pageState.searchOptions.recursive ? 'true' : 'false');
 
+        // Pass group-by-model mode to backend
+        if (state.global.settings.group_by_model) {
+            params.append('group_by_model', 'true');
+        }
+
         if (!isExcludedView && pageState.filters) {
             if (pageState.filters.tags && Object.keys(pageState.filters.tags).length > 0) {
                 Object.entries(pageState.filters.tags).forEach(([tag, state]) => {