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/java/com/hawhamburg/micr0bu/MainActivity.kt

@@ -1,8 +1,11 @@
 package com.hawhamburg.micr0bu
 
 import android.Manifest
+import android.content.Intent
+import android.net.Uri
 import android.os.Build
 import android.os.Bundle
+import android.provider.Settings
 import androidx.core.splashscreen.SplashScreen.Companion.installSplashScreen
 import androidx.appcompat.app.AppCompatActivity
 import androidx.activity.SystemBarStyle
@@ -46,6 +49,7 @@ import com.hawhamburg.micr0bu.ui.screens.MqttSettingsScreen
 import com.hawhamburg.micr0bu.ui.screens.SensorsSettingsScreen
 import com.hawhamburg.micr0bu.ui.screens.SettingsScreen
 import com.hawhamburg.micr0bu.ui.screens.UnitsSettingsScreen
+import com.hawhamburg.micr0bu.ui.screens.UseCaseAlertsSettingsScreen
 import com.hawhamburg.micr0bu.ui.theme.MicrOBUTheme
 import com.hawhamburg.micr0bu.viewmodel.MqttViewModel
 import com.hawhamburg.micr0bu.viewmodel.SensorViewModel
@@ -74,7 +78,10 @@ class MainActivity : AppCompatActivity() {
             val activeTransport          by mqttViewModel.activeTransport.collectAsState()
             val usbConnected             by mqttViewModel.usbConnected.collectAsState()
             val obuStationTypeWarning    by mqttViewModel.obuStationTypeWarning.collectAsState()
+            val obuStationType           by mqttViewModel.obuStationType.collectAsState()
             val tripServiceState         by tripViewModel.serviceState.collectAsState()
+            val showBatteryOptPrompt     by tripViewModel.showBatteryOptPrompt.collectAsState()
+            val useCaseEnabledMap        by mqttViewModel.useCaseEnabledMap.collectAsState()
 
             MicrOBUTheme(darkTheme = state.darkTheme) {
                 val view = LocalView.current
@@ -128,6 +135,7 @@ class MainActivity : AppCompatActivity() {
                                 activeTransport = activeTransport,
                                 usbCableConnected = usbConnected,
                                 obuStationTypeWarning = obuStationTypeWarning,
+                                obuStationType = obuStationType,
                                 onNavigateToConnection = { navController.navigate(Screen.Connection.route) },
                                 onNavigateToSensors = {
                                     navController.navigate(Screen.Sensors.route) {
@@ -147,6 +155,7 @@ class MainActivity : AppCompatActivity() {
                                 state = state,
                                 mqttConnectionState = mqttConnectionState,
                                 tripServiceState = tripServiceState,
+                                showBatteryOptPrompt = showBatteryOptPrompt,
                                 onToggleRecording = {
                                     // Start / stop both CSV recording and the event detection service
                                     viewModel.toggleRecording()
@@ -155,6 +164,15 @@ class MainActivity : AppCompatActivity() {
                                 onOpenSessionLog = {
                                     navController.navigate(Screen.Log.route)
                                 },
+                                onOpenBatterySettings = {
+                                    startActivity(
+                                        Intent(Settings.ACTION_REQUEST_IGNORE_BATTERY_OPTIMIZATIONS).apply {
+                                            data = Uri.parse("package:$packageName")
+                                        }
+                                    )
+                                    tripViewModel.recheckBatteryOpt()
+                                },
+                                onDismissBatteryOptPrompt = tripViewModel::dismissBatteryOptPrompt,
                             )
                         }
                         composable(Screen.Log.route) {
@@ -205,10 +223,18 @@ class MainActivity : AppCompatActivity() {
                                 onOpenUnits      = { navController.navigate(Screen.SettingsUnits.route) },
                                 onOpenConnection = { navController.navigate(Screen.SettingsConnection.route) },
                                 onOpenMqtt       = { navController.navigate(Screen.SettingsMqtt.route) },
+                                onOpenUseCaseAlerts = { navController.navigate(Screen.SettingsUseCaseAlerts.route) },
                                 onOpenDeveloper  = { navController.navigate(Screen.SettingsDeveloper.route) },
                                 onOpenAbout      = { navController.navigate(Screen.SettingsAbout.route) },
                             )
                         }
+                        composable(Screen.SettingsUseCaseAlerts.route) {
+                            UseCaseAlertsSettingsScreen(
+                                enabledMap = useCaseEnabledMap,
+                                onToggle   = mqttViewModel::setUseCaseEnabled,
+                                onBack     = { navController.popBackStack() },
+                            )
+                        }
                         composable(Screen.SettingsConnection.route) {
                             ConnectionSettingsScreen(
                                 mqttPrefs         = mqttPrefs,