feat(#146): modale de sélection d'enfant pour rattachement AM/parent.

Recherche dynamique, filtre Sans garde côté AM, confirmation de transfert et détachement préalable pour laisser le point de vigilance places sur l'AM d'origine.

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

frontend/lib/widgets/admin/common/admin_am_edit_modal.dart

@@ -1,7 +1,6 @@
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:p_tits_pas/models/assistante_maternelle_model.dart';
-import 'package:p_tits_pas/models/enfant_admin_model.dart';
 import 'package:p_tits_pas/models/parent_child_summary.dart';
 import 'package:p_tits_pas/utils/am_vigilance.dart';
 import 'package:p_tits_pas/utils/date_display_utils.dart';
@@ -11,6 +10,7 @@ import 'package:p_tits_pas/services/user_service.dart';
 import 'package:p_tits_pas/widgets/admin/common/admin_am_children_capacity_grid.dart';
 import 'package:p_tits_pas/widgets/admin/common/admin_am_photo_frame.dart';
 import 'package:p_tits_pas/widgets/admin/common/admin_child_detail_modal.dart';
+import 'package:p_tits_pas/widgets/admin/common/admin_select_enfant_modal.dart';
 import 'package:p_tits_pas/widgets/admin/common/admin_status_capsule.dart';
 import 'package:p_tits_pas/widgets/admin/common/validation_detail_section.dart';
 import 'package:p_tits_pas/widgets/common/identity_block.dart';
@@ -55,6 +55,10 @@ class _AdminAmEditModalState extends State<AdminAmEditModal>
   late List<ParentChildSummary> _children;
   late Set<String> _baselineChildIds;
 
+  /// Enfants ajoutés localement qui étaient déjà chez une autre AM
+  /// (enfantId → amUserId d'origine). Au save : détacher puis rattacher.
+  final Map<String, String> _transferFromAmIds = {};
+
   bool _saving = false;
   bool _dirty = false;
 
@@ -311,6 +315,17 @@ class _AdminAmEditModalState extends State<AdminAmEditModal>
         );
       }
       for (final id in currentIds.difference(_baselineChildIds)) {
+        // Transfert : détacher l'ancienne AM sans recalculer ses places
+        // (le ! de vigilance apparaît côté liste AM).
+        final previousAmId = _transferFromAmIds[id] ??
+            (await UserService.findAmForEnfant(id))?.user.id;
+        if (previousAmId != null &&
+            previousAmId != widget.assistante.user.id) {
+          await UserService.detachEnfantFromAm(
+            amUserId: previousAmId,
+            enfantId: id,
+          );
+        }
         await UserService.attachEnfantToAm(
           amUserId: widget.assistante.user.id,
           enfantId: id,
@@ -346,6 +361,7 @@ class _AdminAmEditModalState extends State<AdminAmEditModal>
         _dirty = false;
         _saving = false;
         _baselineChildIds = currentIds;
+        _transferFromAmIds.clear();
       });
       widget.onSaved?.call();
       ScaffoldMessenger.of(context).showSnackBar(
@@ -377,6 +393,7 @@ class _AdminAmEditModalState extends State<AdminAmEditModal>
       setState(() {
         _children = kids;
         _baselineChildIds = kids.map((c) => c.id).toSet();
+        _transferFromAmIds.clear();
       });
     } catch (_) {}
   }
@@ -442,55 +459,75 @@ class _AdminAmEditModalState extends State<AdminAmEditModal>
 
     setState(() {
       _children = _children.where((c) => c.id != child.id).toList();
+      _transferFromAmIds.remove(child.id);
       _syncPlacesAfterChildrenChange();
       _dirty = true;
     });
   }
 
   Future<void> _attachChild() async {
-    List<EnfantAdminModel> all;
-    try {
-      all = await UserService.getEnfants();
-    } catch (e) {
-      if (!mounted) return;
-      ScaffoldMessenger.of(context).showSnackBar(
-        SnackBar(content: Text(e.toString().replaceFirst('Exception: ', ''))),
-      );
-      return;
-    }
-
-    final linkedIds = _children.map((c) => c.id).toSet();
-    final candidates = all.where((e) => !linkedIds.contains(e.id)).toList();
-    if (candidates.isEmpty) {
-      if (!mounted) return;
-      ScaffoldMessenger.of(context).showSnackBar(
-        const SnackBar(content: Text('Aucun enfant disponible à rattacher')),
-      );
-      return;
-    }
-
     if (!mounted) return;
-    final selected = await showDialog<EnfantAdminModel>(
-      context: context,
-      builder: (ctx) => SimpleDialog(
-        title: const Text('Rattacher un enfant'),
-        children: candidates
-            .map(
-              (e) => SimpleDialogOption(
-                onPressed: () => Navigator.pop(ctx, e),
-                child: Text(e.fullName),
-              ),
-            )
-            .toList(),
-      ),
+    final selected = await AdminSelectEnfantModal.show(
+      context,
+      excludeIds: _children.map((c) => c.id).toSet(),
+      title: 'Rattacher un enfant',
+      showSansGardeFilter: true,
     );
     if (selected == null || !mounted) return;
 
+    AssistanteMaternelleModel? previousAm;
+    try {
+      previousAm = await UserService.findAmForEnfant(selected.id);
+    } catch (_) {
+      previousAm = null;
+    }
+    if (!mounted) return;
+
+    final previousAmId = previousAm?.user.id;
+    final isTransfer = previousAmId != null &&
+        previousAmId != widget.assistante.user.id;
+
+    if (isTransfer) {
+      final amName = previousAm!.user.fullName.trim().isNotEmpty
+          ? previousAm.user.fullName.trim()
+          : 'une autre assistante maternelle';
+      final gardeLabel =
+          (selected.gender ?? '').trim().toUpperCase() == 'F'
+              ? 'déjà gardée'
+              : 'déjà gardé';
+      final confirmed = await showDialog<bool>(
+        context: context,
+        builder: (ctx) => AlertDialog(
+          title: const Text('Changer d\'affectation'),
+          content: Text(
+            '${selected.fullName} est $gardeLabel par $amName.\n\n'
+            'Confirmer le transfert vers cette assistante ? '
+            'L\'enfant sera détaché de $amName.',
+          ),
+          actions: [
+            TextButton(
+              onPressed: () => Navigator.pop(ctx, false),
+              child: const Text('Annuler'),
+            ),
+            ElevatedButton(
+              onPressed: () => Navigator.pop(ctx, true),
+              style: ValidationModalTheme.primaryElevatedStyle,
+              child: const Text('Confirmer'),
+            ),
+          ],
+        ),
+      );
+      if (confirmed != true || !mounted) return;
+    }
+
     setState(() {
       _children = [
         ..._children,
         ParentChildSummary.fromEnfant(selected),
       ];
+      if (isTransfer) {
+        _transferFromAmIds[selected.id] = previousAmId!;
+      }
       _syncPlacesAfterChildrenChange();
       _dirty = true;
     });