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

rust-port/wifi-densepose-rs/crates/wifi-densepose-nn/src/densepose.rs

@@ -252,7 +252,7 @@ impl DensePoseHead {
         })?;
 
         let input_arr = input.as_array4()?;
-        let (batch, _channels, height, width) = input_arr.dim();
+        let (_batch, _channels, _height, _width) = input_arr.dim();
 
         // Apply shared convolutions
         let mut current = input_arr.clone();