- Loosened the `protobuf` dependency to `>=5.29.6,<7`, so projects pinned to protobuf 5.x can install `pipecat-ai` again. The previous `>=6.31.1,<7` pin (introduced in 1.0.8 alongside the `nvidia-riva-client 2.25.1` upgrade) silently blocked any environment whose dependency graph already constrained protobuf to the 5.x line. The bundled `frames_pb2.py` is now compiled with protoc 5.x so it imports cleanly on both 5.x and 6.x runtimes.

  Installing the `nvidia` extra still pulls protobuf 6.x: `nvidia-riva-client 2.25.1` ships gencode that requires a 6.x runtime, so `pipecat-ai[nvidia]` now declares `protobuf>=6.31.1,<7` explicitly to cover an upstream packaging gap (https://github.com/nvidia-riva/python-clients/issues/172).
