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.

static/js/main.js

@@ -26,7 +26,7 @@ function switchTab(tabName) {
 // Handle URL hash on page load
 if (window.location.hash) {
     const hash = window.location.hash.substring(1);
-    const validTabs = ['home', 'watchlist', 'anime', 'series', 'providers', 'downloads'];
+    const validTabs = ['home', 'watchlist', 'anime', 'series', 'providers', 'downloads', 'settings'];
     if (validTabs.includes(hash)) {
         // Short delay to ensure Alpine is ready
         setTimeout(() => switchTab(hash), 100);
@@ -37,7 +37,7 @@ if (window.location.hash) {
 window.addEventListener('hashchange', function() {
     if (window.location.hash) {
         const hash = window.location.hash.substring(1);
-        const validTabs = ['home', 'watchlist', 'anime', 'series', 'providers', 'downloads'];
+        const validTabs = ['home', 'watchlist', 'anime', 'series', 'providers', 'downloads', 'settings'];
         if (validTabs.includes(hash)) {
             switchTab(hash);
         }