feat: Implement scroll position management with a new setting, add a back-to-top button, and extend search cache duration.

lib/store/settings-store.ts

@@ -46,6 +46,7 @@ export interface AppSettings {
   episodeReverseOrder: boolean; // Persist episode list reverse state
   fullscreenType: 'native' | 'window'; // Fullscreen mode preference
   proxyMode: ProxyMode; // Proxy behavior: 'retry' | 'none' | 'always'
+  rememberScrollPosition: boolean; // Remember scroll position when navigating back or refreshing
 }
 
 import { exportSettings, importSettings, SEARCH_HISTORY_KEY, WATCH_HISTORY_KEY } from './settings-helpers';
@@ -119,6 +120,7 @@ function getDefaultAppSettings(): AppSettings {
     episodeReverseOrder: false,
     fullscreenType: 'native',
     proxyMode: 'retry',
+    rememberScrollPosition: true,
   };
 }
 
@@ -196,6 +198,7 @@ export const settingsStore = {
         episodeReverseOrder: parsed.episodeReverseOrder !== undefined ? parsed.episodeReverseOrder : false,
         fullscreenType: parsed.fullscreenType === 'window' ? 'window' : 'native',
         proxyMode: (parsed.proxyMode === 'retry' || parsed.proxyMode === 'none' || parsed.proxyMode === 'always') ? parsed.proxyMode : 'retry',
+        rememberScrollPosition: parsed.rememberScrollPosition !== undefined ? parsed.rememberScrollPosition : true,
       };
     } catch {
       // Even if localStorage fails, we should return defaults + ENV subscriptions