feat: CAM-based use case detection engine, decouple DENM from sensor triggers

Added:
- UseCaseDetectionEngine: IMA-B, IMA-S, RTW-B, LTW-B, SMVA/BCW-B via per-station
  CAM history, yaw-rate/heading-trend turn detection, Info/Awareness/Warning alerts
- Ego state from obu_gnss (~4Hz, yaw rate) with phone GPS fallback when stale
- Human-readable alert narratives + technical detail in V2X Monitor
- Settings > Use Case Alerts per-use-case toggles

Fixed:
- DENM no longer auto-fires on braking/stopping; manual-only (antenna/RSU test)
- Removed unwired CamBuilder.kt (dead code, contradicted CAM-only architecture)
- TripRecordingService no longer depends on MQTT/OBU connectivity

app/src/main/AndroidManifest.xml

@@ -5,6 +5,8 @@
     <uses-permission android:name="android.permission.INTERNET" />
     <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />
     <uses-permission android:name="android.permission.CHANGE_NETWORK_STATE" />
+    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
+    <uses-permission android:name="android.permission.CHANGE_WIFI_STATE" />
 
     <!-- Location -->
     <uses-permission android:name="android.permission.ACCESS_FINE_LOCATION" />
@@ -21,6 +23,10 @@
     <!-- Keep CPU active while recording with screen off -->
     <uses-permission android:name="android.permission.WAKE_LOCK" />
 
+    <!-- Allows prompting the user to exempt this app from battery optimization
+         so GPS callbacks are not throttled when the screen is off during a trip. -->
+    <uses-permission android:name="android.permission.REQUEST_IGNORE_BATTERY_OPTIMIZATIONS" />
+
     <uses-feature android:name="android.hardware.sensor.accelerometer" android:required="false" />
     <uses-feature android:name="android.hardware.sensor.gyroscope"     android:required="false" />
     <uses-feature android:name="android.hardware.sensor.compass"       android:required="false" />