fix(fitness): request ACTIVITY_RECOGNITION for cadence

Android step detector silently returns no events on API 29+
when ACTIVITY_RECOGNITION is ungranted, so cadence was always
absent from recorded tracks. Declare the permission, request
it at GPS start, guard sensor registration and retry it from
MainActivity.onRequestPermissionsResult when the user grants
mid-session, and toast a hint if they deny.

src-tauri/gen/android/app/src/main/AndroidManifest.xml

@@ -9,6 +9,8 @@
     <uses-permission android:name="android.permission.POST_NOTIFICATIONS" />
     <uses-permission android:name="android.permission.CAMERA" />
     <uses-permission android:name="android.permission.VIBRATE" />
+    <!-- Step detector sensor (cadence during GPS workouts); runtime-requested on API 29+ -->
+    <uses-permission android:name="android.permission.ACTIVITY_RECOGNITION" />
 
     <!-- AndroidTV support -->
     <uses-feature android:name="android.software.leanback" android:required="false" />

src-tauri/gen/android/app/src/main/java/org/bocken/app/AndroidBridge.kt

@@ -20,6 +20,12 @@ import java.util.Locale
 
 class AndroidBridge(private val context: Context) {
 
+    companion object {
+        const val REQ_BACKGROUND_LOCATION = 1002
+        const val REQ_NOTIFICATIONS = 1003
+        const val REQ_ACTIVITY_RECOGNITION = 1004
+    }
+
     @JavascriptInterface
     fun startLocationService(ttsConfigJson: String, startPaused: Boolean) {
         if (context is Activity) {
@@ -31,7 +37,7 @@ class AndroidBridge(private val context: Context) {
                     ActivityCompat.requestPermissions(
                         context,
                         arrayOf(Manifest.permission.POST_NOTIFICATIONS),
-                        1003
+                        REQ_NOTIFICATIONS
                     )
                 }
             }
@@ -44,7 +50,20 @@ class AndroidBridge(private val context: Context) {
                     ActivityCompat.requestPermissions(
                         context,
                         arrayOf(Manifest.permission.ACCESS_BACKGROUND_LOCATION),
-                        1002
+                        REQ_BACKGROUND_LOCATION
+                    )
+                }
+            }
+
+            // Request activity recognition on Android 10+ (required for step detector / cadence)
+            if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.Q) {
+                if (ContextCompat.checkSelfPermission(context, Manifest.permission.ACTIVITY_RECOGNITION)
+                    != PackageManager.PERMISSION_GRANTED
+                ) {
+                    ActivityCompat.requestPermissions(
+                        context,
+                        arrayOf(Manifest.permission.ACTIVITY_RECOGNITION),
+                        REQ_ACTIVITY_RECOGNITION
                     )
                 }
             }
@@ -104,6 +123,15 @@ class AndroidBridge(private val context: Context) {
         return LocationForegroundService.getIntervalState()
     }
 
+    /** True if cadence (step detector) is usable — permission granted or not required (pre-Q). */
+    @JavascriptInterface
+    fun hasActivityRecognitionPermission(): Boolean {
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.Q) return true
+        return ContextCompat.checkSelfPermission(
+            context, Manifest.permission.ACTIVITY_RECOGNITION
+        ) == PackageManager.PERMISSION_GRANTED
+    }
+
     /**
      * Force-vibrate bypassing silent/DND by using USAGE_ACCESSIBILITY attributes.
      * Why: default web Vibration API uses USAGE_TOUCH which Android silences.

src-tauri/gen/android/app/src/main/java/org/bocken/app/LocationForegroundService.kt

@@ -4,9 +4,11 @@ import android.app.Notification
 import android.app.NotificationChannel
 import android.app.NotificationManager
 import android.app.PendingIntent
+import android.Manifest
 import android.app.Service
 import android.content.Context
 import android.content.Intent
+import android.content.pm.PackageManager
 import android.hardware.Sensor
 import android.hardware.SensorEvent
 import android.hardware.SensorEventListener
@@ -24,6 +26,7 @@ import android.os.Looper
 import android.speech.tts.TextToSpeech
 import android.speech.tts.UtteranceProgressListener
 import android.util.Log
+import androidx.core.content.ContextCompat
 import org.json.JSONArray
 import org.json.JSONObject
 import java.util.Collections
@@ -696,8 +699,22 @@ class LocationForegroundService : Service(), TextToSpeech.OnInitListener, Sensor
         notificationManager?.notify(NOTIFICATION_ID, notification)
     }
 
+    private fun hasActivityRecognitionPermission(): Boolean {
+        if (Build.VERSION.SDK_INT < Build.VERSION_CODES.Q) return true
+        return ContextCompat.checkSelfPermission(
+            this, Manifest.permission.ACTIVITY_RECOGNITION
+        ) == PackageManager.PERMISSION_GRANTED
+    }
+
     private fun startStepDetector() {
-        sensorManager = getSystemService(Context.SENSOR_SERVICE) as SensorManager
+        if (!hasActivityRecognitionPermission()) {
+            Log.d(TAG, "Step detector skipped — ACTIVITY_RECOGNITION not granted")
+            return
+        }
+        if (stepDetector != null) return // already registered
+        if (sensorManager == null) {
+            sensorManager = getSystemService(Context.SENSOR_SERVICE) as SensorManager
+        }
         stepDetector = sensorManager?.getDefaultSensor(Sensor.TYPE_STEP_DETECTOR)
         if (stepDetector != null) {
             sensorManager?.registerListener(this, stepDetector, SensorManager.SENSOR_DELAY_FASTEST)
@@ -707,6 +724,12 @@ class LocationForegroundService : Service(), TextToSpeech.OnInitListener, Sensor
         }
     }
 
+    /** Called from MainActivity when ACTIVITY_RECOGNITION is granted mid-session. */
+    fun onActivityRecognitionGranted() {
+        Log.d(TAG, "ACTIVITY_RECOGNITION granted — retrying step detector registration")
+        startStepDetector()
+    }
+
     @Suppress("MissingPermission")
     private fun startLocationUpdates() {
         locationManager = getSystemService(Context.LOCATION_SERVICE) as LocationManager

src-tauri/gen/android/app/src/main/java/org/bocken/app/MainActivity.kt

@@ -1,5 +1,6 @@
 package org.bocken.app
 
+import android.content.pm.PackageManager
 import android.os.Bundle
 import android.webkit.WebView
 import androidx.activity.enableEdgeToEdge
@@ -13,4 +14,17 @@ class MainActivity : TauriActivity() {
   override fun onWebViewCreate(webView: WebView) {
     webView.addJavascriptInterface(AndroidBridge(this), "AndroidBridge")
   }
+
+  override fun onRequestPermissionsResult(
+    requestCode: Int,
+    permissions: Array<out String>,
+    grantResults: IntArray
+  ) {
+    super.onRequestPermissionsResult(requestCode, permissions, grantResults)
+    if (requestCode == AndroidBridge.REQ_ACTIVITY_RECOGNITION &&
+        grantResults.isNotEmpty() &&
+        grantResults[0] == PackageManager.PERMISSION_GRANTED) {
+      LocationForegroundService.instance?.onActivityRecognitionGranted()
+    }
+  }
 }