docs: Add comprehensive wifi-Mat user guide and fix compilation

- Add detailed wifi-Mat user guide covering:
  - Installation and setup
  - Detection capabilities (breathing, heartbeat, movement)
  - Localization system (triangulation, depth estimation)
  - START protocol triage classification
  - Alert system with priority escalation
  - Field deployment guide
  - Hardware setup requirements
  - API reference and troubleshooting

- Update main README.md with wifi-Mat section and links

- Fix compilation issues:
  - Add missing deadline field in AlertPayload
  - Fix type ambiguity in powi calls
  - Resolve borrow checker issues in scan_cycle
  - Export CsiDataBuffer from detection module
  - Add missing imports in test modules

- All 83 tests now passing

rust-port/wifi-densepose-rs/crates/wifi-densepose-mat/src/domain/alert.rs

@@ -130,6 +130,7 @@ impl AlertPayload {
             triage_status,
             location: None,
             recommended_action: String::new(),
+            deadline: None,
             metadata: std::collections::HashMap::new(),
         }
     }