iOS: Share Extension (share to Noo) via an App Group inbox

ShareExtension target copies shared files into group.dev.ayushya.noo and
leaves a manifest; the app consumes it on launch/activation through the
existing share_intent channel into the destination picker. Extension is
embedded before Flutter's script phases; versions follow FLUTTER_BUILD_*.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

ios/Runner/Native/TransferManager.swift

@@ -100,6 +100,11 @@ final class TransferManager: NSObject {
       let staged = stageDir.appendingPathComponent("\(index)-\(file.name)")
       do {
         try FileManager.default.copyItem(at: source, to: staged)
+        // A file the Share Extension left in the App Group is ours to clean
+        // up once it's staged; a picker's temp file isn't.
+        if source.path.contains("/\(SharedInbox.folderName)/") {
+          try? FileManager.default.removeItem(at: source)
+        }
       } catch {
         throw TransferError(message: "Can't read \(file.name): \(error.localizedDescription)")
       }