fix: complete sensing server API, WebSocket connectivity, and mobile tests (#125)

The web UI had persistent 404 errors on model, recording, and training
endpoints, and the sensing WebSocket never connected on Dashboard/Live
Demo tabs because sensingService.start() was only called lazily on
Sensing tab visit.

Server (main.rs):
- Add 14 fully-functional Axum handlers: model CRUD (7), recording
  lifecycle (4), training control (3)
- Scan data/models/ and data/recordings/ at startup
- Recording writes CSI frames to .jsonl via tokio background task
- Model load/unload lifecycle with state tracking

Web UI (app.js):
- Import and start sensingService early in initializeServices() so
  Dashboard and Live Demo tabs connect to /ws/sensing immediately

Mobile (ws.service.ts):
- Fix WebSocket URL builder to use same-origin port instead of
  hardcoded port 3001

Mobile (jest.config.js):
- Fix testPathIgnorePatterns that was ignoring the entire test directory

Mobile (25 test files):
- Replace all it.todo() placeholder tests with real implementations
  covering components, services, stores, hooks, screens, and utils

ADR-043 documents all changes.

ui/app.js

@@ -8,6 +8,7 @@ import { SensingTab } from './components/SensingTab.js';
 import { apiService } from './services/api.service.js';
 import { wsService } from './services/websocket.service.js';
 import { healthService } from './services/health.service.js';
+import { sensingService } from './services/sensing.service.js';
 import { backendDetector } from './utils/backend-detector.js';
 
 class WiFiDensePoseApp {
@@ -75,6 +76,10 @@ class WiFiDensePoseApp {
         console.warn('⚠️ Backend not available:', error.message);
         this.showBackendStatus('Backend unavailable — start sensing-server', 'warning');
       }
+
+      // Start the sensing WebSocket service early so the dashboard and
+      // live-demo tabs can show the correct data-source status immediately.
+      sensingService.start();
     }
   }