feat(tv): implement fullscreen navigation behavior for TV page

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

@@ -79,6 +79,14 @@ export default function TvPage() {
     document.addEventListener("fullscreenchange", handler);
     return () => document.removeEventListener("fullscreenchange", handler);
   }, []);
+
+  // Hide the shared nav bar in fullscreen; reveal it when overlays are shown
+  // (mouse move / key press). Classes are cleaned up on unmount.
+  useEffect(() => {
+    document.body.classList.toggle("tv-fullscreen", isFullscreen);
+    document.body.classList.toggle("tv-overlays", isFullscreen && showOverlays);
+    return () => document.body.classList.remove("tv-fullscreen", "tv-overlays");
+  }, [isFullscreen, showOverlays]);
   const toggleFullscreen = useCallback(() => {
     if (!document.fullscreenElement) {
       document.documentElement.requestFullscreen().catch(() => {});