fix(download): preserve SAF and defer background starts

android/app/src/main/kotlin/com/zarz/spotiflac/ForegroundServiceStartPolicy.kt

@@ -0,0 +1,18 @@
+package com.zarz.spotiflac
+
+/** Maps Android/OEM foreground-service launch denials to a stable Dart code. */
+object ForegroundServiceStartPolicy {
+    const val START_NOT_ALLOWED_CODE = "foreground_service_start_not_allowed"
+
+    fun isStartNotAllowed(error: Throwable): Boolean {
+        if (error.javaClass.name == "android.app.ForegroundServiceStartNotAllowedException") {
+            return true
+        }
+        val message = error.message.orEmpty()
+        return message.contains("startForegroundService() not allowed", ignoreCase = true) ||
+            message.contains("mAllowStartForeground false", ignoreCase = true)
+    }
+
+    fun errorCode(error: Throwable): String =
+        if (isStartNotAllowed(error)) START_NOT_ALLOWED_CODE else "ERROR"
+}

android/app/src/main/kotlin/com/zarz/spotiflac/MainActivity.kt

@@ -2326,7 +2326,11 @@ class MainActivity: FlutterFragmentActivity() {
                         else -> result.notImplemented()
                     }
                 } catch (e: Exception) {
-                    result.error("ERROR", e.message, null)
+                    result.error(
+                        ForegroundServiceStartPolicy.errorCode(e),
+                        e.message,
+                        null,
+                    )
                 }
             }
         }

android/app/src/test/kotlin/com/zarz/spotiflac/ForegroundServiceStartPolicyTest.kt

@@ -0,0 +1,29 @@
+package com.zarz.spotiflac
+
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertFalse
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+class ForegroundServiceStartPolicyTest {
+    @Test
+    fun mapsAndroidForegroundStartDenialsToStableCode() {
+        val error = IllegalStateException(
+            "startForegroundService() not allowed due to mAllowStartForeground false",
+        )
+
+        assertTrue(ForegroundServiceStartPolicy.isStartNotAllowed(error))
+        assertEquals(
+            ForegroundServiceStartPolicy.START_NOT_ALLOWED_CODE,
+            ForegroundServiceStartPolicy.errorCode(error),
+        )
+    }
+
+    @Test
+    fun leavesUnrelatedPlatformFailuresGeneric() {
+        val error = IllegalStateException("network unavailable")
+
+        assertFalse(ForegroundServiceStartPolicy.isStartNotAllowed(error))
+        assertEquals("ERROR", ForegroundServiceStartPolicy.errorCode(error))
+    }
+}