[feat] update some feature

sync code of  fastrtc,
add text support through datachannel,
fix safari connect problem
support chat without camera or mic

backend/fastrtc/pause_detection/protocol.py

@@ -0,0 +1,20 @@
+from typing import Any, Protocol, TypeAlias
+
+import numpy as np
+from numpy.typing import NDArray
+
+from ..utils import AudioChunk
+
+ModelOptions: TypeAlias = Any
+
+
+class PauseDetectionModel(Protocol):
+    def vad(
+        self,
+        audio: tuple[int, NDArray[np.int16] | NDArray[np.float32]],
+        options: ModelOptions,
+    ) -> tuple[float, list[AudioChunk]]: ...
+
+    def warmup(
+        self,
+    ) -> None: ...