feat: add Settings tab with provider management and language preferences

- Implemented AppSettings model and table using SQLModel.
- Created Settings router with endpoints for preferences and provider toggling.
- Added Settings tab to the UI with real-time health status of providers.
- Integrated language and provider filtering into anime and series search logic.
- Updated templates to respect user-defined settings.

templates/index.html

@@ -142,6 +142,14 @@
 {% include "components/downloads_section.html" %}
 </div>
 
+<div id="tab-settings" class="tab-content" x-show="activeTab === 'settings'">
+    <div hx-get="/api/settings/ui" hx-trigger="load, set-tab[detail.tab === 'settings'] from:window" hx-swap="innerHTML">
+        <div class="loading-placeholder">
+            <div class="spinner"></div> Chargement des paramètres...
+        </div>
+    </div>
+</div>
+
 </div>
 <!-- End of main-content -->