redisign multiple payouts for better ux and small fixes

frontend/pweb/lib/services/payments/csv_input.dart

@@ -19,17 +19,11 @@ class WebCsvInputService implements CsvInputService {
   Future<PickedCsvFile?> pickCsv() async {
     final input = html.FileUploadInputElement()
       ..accept = '.csv,text/csv'
-      ..multiple = false;
+      ..multiple = false
+      ..style.display = 'none';
 
-    final completer = Completer<html.File?>();
-    input.onChange.listen((_) {
-      completer.complete(
-        input.files?.isNotEmpty == true ? input.files!.first : null,
-      );
-    });
-    input.click();
-
-    final file = await completer.future;
+    html.document.body?.append(input);
+    final file = await _pickFile(input);
     if (file == null) return null;
 
     final reader = html.FileReader();
@@ -50,4 +44,52 @@ class WebCsvInputService implements CsvInputService {
     final content = await readCompleter.future;
     return PickedCsvFile(name: file.name, content: content);
   }
+
+  Future<html.File?> _pickFile(html.FileUploadInputElement input) async {
+    final completer = Completer<html.File?>();
+
+    void completeWith(html.File? file) {
+      if (!completer.isCompleted) completer.complete(file);
+    }
+
+    StreamSubscription<html.Event>? changeSub;
+    StreamSubscription<html.Event>? inputSub;
+    StreamSubscription<html.Event>? focusSub;
+    Timer? timeout;
+
+    void cleanup() {
+      changeSub?.cancel();
+      inputSub?.cancel();
+      focusSub?.cancel();
+      timeout?.cancel();
+      input.remove();
+    }
+
+    void tryComplete() {
+      final file = input.files?.isNotEmpty == true ? input.files!.first : null;
+      if (file != null) {
+        completeWith(file);
+      }
+    }
+
+    changeSub = input.onChange.listen((_) => tryComplete());
+    inputSub = input.onInput.listen((_) => tryComplete());
+    focusSub = html.window.onFocus.listen((_) async {
+      if (completer.isCompleted) return;
+      for (var i = 0; i < 6; i++) {
+        tryComplete();
+        if (completer.isCompleted) return;
+        await Future<void>.delayed(const Duration(milliseconds: 120));
+      }
+      if (!completer.isCompleted && (input.value ?? '').isEmpty) {
+        completeWith(null);
+      }
+    });
+
+    timeout = Timer(const Duration(minutes: 2), () => completeWith(null));
+
+    completer.future.whenComplete(cleanup);
+    input.click();
+    return completer.future;
+  }
 }