fix: Clean up Rust warnings and add Python vital signs detection
Rust changes:
- Fix unused variable warnings in wifi-densepose-nn (densepose.rs, inference.rs, tensor.rs, translator.rs)
- Remove unused imports in wifi-densepose-mat (breathing.rs, pipeline.rs, csi_receiver.rs, debris_model.rs, vital_signs_classifier.rs)
- All tests continue to pass
Python changes:
- Add vital_signs.py module with BreathingDetector and HeartbeatDetector classes
- Mirror Rust wifi-densepose-mat detection functionality
- Update v1 package version to 1.2.0
- Export new vital signs classes from core module
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