Fix video not advancing + media not downloading on same-version startup

BUG-009: _on_video_eos was empty (stub). Added Clock.schedule_once
for next_media() when video reaches end of stream.

BUG-008: download_media_files only ran when server_version >
local_version. Added download check in up-to-date branch so media
files are synced even when playlist version hasn't changed.

src/main.py

@@ -1522,6 +1522,9 @@ class SignagePlayer(Widget):
     def _on_video_eos(self, instance):
         """Callback when video reaches end of stream"""
         Logger.debug("SignagePlayer: Video finished playing (EOS)")
+        # Unschedule any pending timer and advance to next media
+        Clock.unschedule(self.next_media)
+        Clock.schedule_once(self.next_media, 0.5)
     
     def _on_video_loaded(self, instance, value):
         """Callback when video is loaded - log video information"""