fix: align spatius avatar eof and runtime compatibility

[3DRX]

Summary

• switch Spatius avatar EOF handling from tts_audio_end data to the drain command
• update the Spatius avatar manifest to accept drain and stop declaring tts_audio_end input
• bump spatius_avatar_python to 0.1.3 and update local avatar base docs
• update Spatius SDK dependency to spatius==1.0.2 and constrain protobuf to >=5.28.3,<6 for TEN runtime compatibility
• use ten_ai_base.utils.encrypt for Spatius API key, Agora token, and Agora app certificate in config logs

Tests

• uvx --from black black --check --line-length 80 ai_agents/agents/ten_packages/extension/spatius_avatar_python/avatar_base.py ai_agents/agents/ten_packages/extension/spatius_avatar_python/extension.py
• python3 -m py_compile ai_agents/agents/ten_packages/extension/spatius_avatar_python/avatar_base.py ai_agents/agents/ten_packages/extension/spatius_avatar_python/extension.py
• python3 -m venv /private/tmp/spatius-ten-req-venv && /private/tmp/spatius-ten-req-venv/bin/python -m pip install -q -r ai_agents/agents/ten_packages/extension/spatius_avatar_python/requirements.txt && /private/tmp/spatius-ten-req-venv/bin/python - <<'PY'
  import google.protobuf
  import spatius
  from spatius.proto.generated import message_pb2
  print('protobuf', google.protobuf.version)
  print('spatius', spatius.name)
  print('message', message_pb2.Message.DESCRIPTOR.full_name)
  PY

Note: full container task check was not run because ten_agent_dev is not running locally.