feat(tv-page): add subtitle track toggle functionality

k-tv-frontend/app/(main)/tv/page.tsx

@@ -429,6 +429,14 @@ function TvPageContent() {
         case "M":
           toggleMute();
           break;
+        case "c":
+        case "C":
+          if (subtitleTracks.length > 0) {
+            setActiveSubtitleTrack((prev) =>
+              prev === -1 ? subtitleTracks[0].id : -1,
+            );
+          }
+          break;
         default: {
           if (e.key >= "0" && e.key <= "9") {
             setChannelInput((prev) => {
@@ -464,6 +472,7 @@ function TvPageContent() {
     channelCount,
     switchChannel,
     resetIdle,
+    subtitleTracks,
   ]);
 
   // ------------------------------------------------------------------