v1.0.56: allow root folder selection + MANAGE_EXTERNAL_STORAGE prompt

Remove root folder block from the browser — user can now select
/storage/emulated/0 exactly like Autosync. If MANAGE_EXTERNAL_STORAGE
is not granted a red banner appears with a direct "Grant" button that
opens the Android All files access settings screen. Root guard removed
from SyncEngine; individual file failures (e.g. root-level writes) are
already caught and logged per-file.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/src/main/kotlin/com/syncflow/domain/sync/SyncEngine.kt

@@ -34,17 +34,6 @@ class SyncEngine @Inject constructor(
     @ApplicationContext private val context: Context,
 ) {
     suspend fun sync(pair: SyncPair, provider: CloudProvider): SyncResult {
-        if (!pair.localPath.startsWith("content://") &&
-            pair.syncDirection != SyncDirection.UPLOAD_ONLY) {
-            val canonical = runCatching { File(pair.localPath).canonicalPath }.getOrElse { pair.localPath }
-            if (canonical == "/storage/emulated/0") {
-                val msg = "Local folder is the storage root — Android blocks writes here. Use Upload Only direction, or select a subfolder."
-                syncPairDao.updateSyncResult(pair.id, Instant.now(), SyncStatus.FAILED, 0)
-                logEvent(pair.id, SyncEventType.SYNC_FAILED, null, msg, 0)
-                return SyncResult(failedFiles = 1, error = Exception(msg))
-            }
-        }
-
         syncPairDao.updateStatus(pair.id, SyncStatus.SYNCING)
         logEvent(pair.id, SyncEventType.SYNC_STARTED, null, null, 0)