feat: update folder selection to use SafInitialUris for improved document access

app/src/main/java/at/lockstep/player/util/SafInitialUris.kt

@@ -0,0 +1,15 @@
+package at.lockstep.player.util
+
+import android.net.Uri
+import android.provider.DocumentsContract
+
+object SafInitialUris {
+    private const val EXTERNAL_STORAGE_AUTHORITY = "com.android.externalstorage.documents"
+
+    /** Internal-storage Documents — avoids the blocked volume root shown on Pixel devices. */
+    fun internalDocuments(): Uri =
+        DocumentsContract.buildDocumentUri(
+            EXTERNAL_STORAGE_AUTHORITY,
+            "primary:Documents",
+        )
+}