Inline local-smart-turn-v3 deps for Poetry compatibility

Replace self-referential `pipecat-ai[local-smart-turn-v3]` extra in core
dependencies with the actual packages (`transformers`, `onnxruntime`).
Self-referential extras are not supported by Poetry and cause dependency
resolution failures. Since these are required by the default turn stop
strategy (LocalSmartTurnAnalyzerV3), they belong in core dependencies.

- Remove `local-smart-turn-v3` optional extra from pyproject.toml
- Remove try/except ModuleNotFoundError guard (now always installed)
- Remove `--extra local-smart-turn-v3` from CI workflows

.github/workflows/coverage.yaml

@@ -40,7 +40,6 @@ jobs:
             --extra google \
             --extra langchain \
             --extra livekit \
-            --extra local-smart-turn-v3 \
             --extra piper \
             --extra tracing \
             --extra websocket