feat(rtc): add restart_publisher method stub to Room

Add `restart_publisher()` method stub to the Room class. This method will
perform an ICE restart on the publisher PeerConnection when implemented.

Use case: When sending data (stream_text/publish_data) times out but receiving
audio/video continues to work, the publisher PeerConnection may be stuck.
Currently there's no way to recover without disconnecting the entire room.

This is a placeholder that raises NotImplementedError until the corresponding
FFI bindings are added to livekit/rust-sdks.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: Hormold

livekit-rtc/livekit/rtc/room.py

@@ -541,6 +541,34 @@ async def get_rtc_stats(self) -> RtcStats:
 
         return RtcStats(publisher_stats=publisher_stats, subscriber_stats=subscriber_stats)
 
+    async def restart_publisher(self) -> None:
+        """Restart the publisher PeerConnection with an ICE restart.
+
+        This is useful when the publisher connection fails while the subscriber still works.
+        For example, when sending data (stream_text/publish_data) times out but receiving
+        audio/video still works.
+
+        Raises:
+            NotImplementedError: This method requires FFI bindings in rust-sdks.
+                See: https://github.com/livekit/rust-sdks/issues/XXX
+
+        Example:
+            ```python
+            try:
+                await room.local_participant.publish_data(data)
+            except TimeoutError:
+                # Publisher might be stuck, try to restart it
+                await room.restart_publisher()
+                # Retry the operation
+                await room.local_participant.publish_data(data)
+            ```
+        """
+        raise NotImplementedError(
+            "restart_publisher() requires FFI bindings in livekit/rust-sdks. "
+            "This is a placeholder for future implementation. "
+            "See: https://github.com/livekit/python-sdks/pull/571"
+        )
+
     def register_byte_stream_handler(self, topic: str, handler: ByteStreamHandler):
         existing_handler = self._byte_stream_handlers.get(topic)
         if existing_handler is None: