feat(appearance): episode images for Next Up & Continue Watching

- Fix black episode thumbnails in the Next Up / Continue Watching rows:
  build the parent Thumb URL from the matched ParentThumbItemId +
  ParentThumbImageTag pair, instead of pairing ParentBackdropItemId with
  the thumb tag (different parent -> 404 -> black). Fixed on mobile
  (ContinueWatchingPoster) and TV (TVPosterCard, TVHeroCarousel).
- Add a "Use episode images for Next Up & Continue Watching" setting
  (default off = series image, matching Jellyfin), wired into the home
  rows on mobile and TV.
- Add helper descriptions under the Appearance settings rows.

components/settings/AppearanceSettings.tsx

@@ -28,6 +28,7 @@ export const AppearanceSettings: React.FC = () => {
       <ListGroup title={t("home.settings.appearance.title")} className=''>
         <ListItem
           title={t("home.settings.other.show_custom_menu_links")}
+          subtitle={t("home.settings.other.show_custom_menu_links_hint")}
           disabled={pluginSettings?.showCustomMenuLinks?.locked}
           onPress={() =>
             Linking.openURL(
@@ -45,6 +46,9 @@ export const AppearanceSettings: React.FC = () => {
         </ListItem>
         <ListItem
           title={t("home.settings.appearance.merge_next_up_continue_watching")}
+          subtitle={t(
+            "home.settings.appearance.merge_next_up_continue_watching_hint",
+          )}
         >
           <SettingSwitch
             value={settings.mergeNextUpAndContinueWatching}
@@ -53,8 +57,24 @@ export const AppearanceSettings: React.FC = () => {
             }
           />
         </ListItem>
+        <ListItem
+          title={t("home.settings.appearance.use_episode_images_next_up")}
+          subtitle={t(
+            "home.settings.appearance.use_episode_images_next_up_hint",
+          )}
+        >
+          <SettingSwitch
+            value={settings.useEpisodeImagesForNextUp}
+            onValueChange={(value) =>
+              updateSettings({ useEpisodeImagesForNextUp: value })
+            }
+          />
+        </ListItem>
         <ListItem
           title={t("home.settings.appearance.hide_remote_session_button")}
+          subtitle={t(
+            "home.settings.appearance.hide_remote_session_button_hint",
+          )}
         >
           <SettingSwitch
             value={settings.hideRemoteSessionButton}
@@ -68,6 +88,7 @@ export const AppearanceSettings: React.FC = () => {
             router.push("/settings/appearance/hide-libraries/page")
           }
           title={t("home.settings.other.hide_libraries")}
+          subtitle={t("home.settings.other.select_libraries_you_want_to_hide")}
           showArrow
         />
       </ListGroup>