fix: auto-reset serviceFailed on permission re-grant, document source column

LocationServiceCoordinator:
- Add resetFailedState() method
- acquire() checks permission when serviceFailed is true and resets
  automatically if re-granted (no process restart needed)

ReceivedLocationEntity:
- Document that source column is scaffolding for future SOS trail
  entries (PR torlando-tech#713)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: MatthieuTexier

app/src/main/java/network/columba/app/service/LocationServiceCoordinator.kt

@@ -20,14 +20,26 @@ object LocationServiceCoordinator {
 
     // Set when the service fails to start (e.g. SecurityException on Android 14+).
     // Prevents observers from retrying acquire() in a loop.
-    // Reset when the user re-grants permission and the app is restarted.
     @Volatile
     private var serviceFailed = false
 
     fun isAcquired(reason: String): Boolean = synchronized(activeReasons) { reason in activeReasons }
 
+    /** Call after the user re-grants location permission to allow re-acquiring the service. */
+    fun resetFailedState() {
+        serviceFailed = false
+        Log.d(TAG, "serviceFailed flag cleared — permission likely re-granted")
+    }
+
     fun acquire(context: Context, reason: String) {
-        if (serviceFailed) return
+        if (serviceFailed) {
+            // Check if permission was re-granted since the failure
+            if (com.lxmf.messenger.util.LocationPermissionManager.hasPermission(context)) {
+                resetFailedState()
+            } else {
+                return
+            }
+        }
         synchronized(activeReasons) {
             val wasEmpty = activeReasons.isEmpty()
             activeReasons.add(reason)

data/src/main/java/network/columba/app/data/db/entity/ReceivedLocationEntity.kt

@@ -38,5 +38,6 @@ data class ReceivedLocationEntity(
 ) {
     companion object {
         const val SOURCE_LOCATION_SHARING = "location_sharing"
+        // Future: SOURCE_SOS_TRAIL = "sos_trail" for SOS breadcrumb trail entries (see PR #713)
     }
 }