feat(front): câbler PATCH refus utilisateur depuis wizards validation (#110)

- UserService.refuseUser → /users/:id/refuser
- AM + famille : envoi motifs, onSuccess + refresh liste
- Famille : refus séquentiel pour chaque parent en_attente
- ValidationRefusForm : état isSubmitting (UX)

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/lib/widgets/admin/validation_refus_form.dart

@@ -8,12 +8,15 @@ class ValidationRefusForm extends StatefulWidget {
   /// Retour à l’étape précédente du wizard (écran avec Valider / Refuser).
   final VoidCallback onPrevious;
   final ValueChanged<String?> onSubmit;
+  /// Pendant l'appel API : désactive les actions (ticket #110).
+  final bool isSubmitting;
 
   const ValidationRefusForm({
     super.key,
     required this.onCancel,
     required this.onPrevious,
     required this.onSubmit,
+    this.isSubmitting = false,
   });
 
   @override
@@ -67,6 +70,7 @@ class _ValidationRefusFormState extends State<ValidationRefusForm> {
                   ),
                   child: TextFormField(
                     controller: _controller,
+                    readOnly: widget.isSubmitting,
                     maxLines: null,
                     minLines: 1,
                     validator: _validateMotifs,
@@ -91,7 +95,7 @@ class _ValidationRefusFormState extends State<ValidationRefusForm> {
           Row(
             children: [
               TextButton(
-                onPressed: widget.onCancel,
+                onPressed: widget.isSubmitting ? null : widget.onCancel,
                 child: const Text('Annuler'),
               ),
               const Spacer(),
@@ -99,19 +103,29 @@ class _ValidationRefusFormState extends State<ValidationRefusForm> {
                 mainAxisSize: MainAxisSize.min,
                 children: [
                   TextButton(
-                    onPressed: widget.onPrevious,
+                    onPressed: widget.isSubmitting ? null : widget.onPrevious,
                     child: const Text('Précédent'),
                   ),
                   const SizedBox(width: 8),
-                  ElevatedButton(
-                    style: ValidationModalTheme.primaryElevatedStyle,
-                    onPressed: () {
-                      if (_formKey.currentState!.validate()) {
-                        widget.onSubmit(_controller.text.trim());
-                      }
-                    },
-                    child: const Text('Envoyer'),
-                  ),
+                  if (widget.isSubmitting)
+                    const Padding(
+                      padding: EdgeInsets.symmetric(horizontal: 12),
+                      child: SizedBox(
+                        width: 22,
+                        height: 22,
+                        child: CircularProgressIndicator(strokeWidth: 2),
+                      ),
+                    )
+                  else
+                    ElevatedButton(
+                      style: ValidationModalTheme.primaryElevatedStyle,
+                      onPressed: () {
+                        if (_formKey.currentState!.validate()) {
+                          widget.onSubmit(_controller.text.trim());
+                        }
+                      },
+                      child: const Text('Envoyer'),
+                    ),
                 ],
               ),
             ],