feat(#152/#155): cleanup est_multiple + dashboard sans préfixe Admin (squash develop).

Suppression complète grossesse multiple / est_multiple (BDD, API, front).
Rename option C : widgets partagés et panels staff sous widgets/dashboard/,
AdminManagementWidget seul restant dans widgets/admin/.

frontend/lib/widgets/dashboard/validation_valider_confirm_dialog.dart

@@ -0,0 +1,32 @@
+import 'package:flutter/material.dart';
+import 'validation_modal_theme.dart';
+
+/// Affiche une confirmation avant d’appeler l’API de validation du dossier.
+/// Retourne `true` si l’utilisateur confirme.
+Future<bool> showValidationValiderConfirmDialog(
+  BuildContext context, {
+  required String body,
+}) async {
+  final result = await showDialog<bool>(
+    context: context,
+    barrierDismissible: false,
+    builder: (dialogContext) {
+      return AlertDialog(
+        title: const Text('Confirmer la validation'),
+        content: Text(body),
+        actions: [
+          TextButton(
+            onPressed: () => Navigator.of(dialogContext).pop(false),
+            child: const Text('Annuler'),
+          ),
+          ElevatedButton(
+            style: ValidationModalTheme.primaryElevatedStyle,
+            onPressed: () => Navigator.of(dialogContext).pop(true),
+            child: const Text('Confirmer'),
+          ),
+        ],
+      );
+    },
+  );
+  return result == true;
+}