feat(#157): alerte enfants sans responsable + rattachement foyer.

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

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

@@ -65,6 +65,9 @@ class _AdminChildDetailModalState extends State<AdminChildDetailModal> {
   /// Famille choisie en mode création (#132).
   AdminFamilleFoyer? _selectedFamily;
 
+  /// Liens parents locaux (édition) — mis à jour après rattachement foyer (#157).
+  List<EnfantParentLink>? _localParentLinks;
+
   /// Photo locale (création) — upload multipart `photo`.
   Uint8List? _photoBytes;
   String? _photoFilename;
@@ -262,10 +265,14 @@ class _AdminChildDetailModalState extends State<AdminChildDetailModal> {
   }
 
   List<EnfantParentLink> get _parentLinks =>
-      (widget.enfant?.parentLinks ?? const <EnfantParentLink>[])
+      (_localParentLinks ??
+              widget.enfant?.parentLinks ??
+              const <EnfantParentLink>[])
           .where((l) => l.parentId.trim().isNotEmpty)
           .toList();
 
+  bool get _isOrphan => !widget.isCreating && _parentLinks.isEmpty;
+
   Future<void> _openParent(EnfantParentLink link) async {
     if (_busy) return;
     final id = link.parentId.trim();
@@ -580,6 +587,7 @@ class _AdminChildDetailModalState extends State<AdminChildDetailModal> {
         if (!enfantStatusValues.contains(_status)) {
           _status = 'sans_garde';
         }
+        _localParentLinks = enfant.parentLinks;
         _coerceGenderForStatus();
       });
     } catch (_) {
@@ -960,7 +968,9 @@ class _AdminChildDetailModalState extends State<AdminChildDetailModal> {
                       padding: const EdgeInsets.only(top: 16),
                       child: Align(
                         alignment: Alignment.bottomCenter,
-                        child: _placementBlock(),
+                        child: SingleChildScrollView(
+                          child: _placementBlock(),
+                        ),
                       ),
                     ),
                   ),
@@ -1219,6 +1229,24 @@ class _AdminChildDetailModalState extends State<AdminChildDetailModal> {
       mainAxisSize: MainAxisSize.min,
       crossAxisAlignment: CrossAxisAlignment.stretch,
       children: [
+        if (_isOrphan) ...[
+          Text(
+            'Sélection du dossier de la famille',
+            style: TextStyle(
+              fontSize: 14,
+              fontWeight: FontWeight.w600,
+              color: Colors.red.shade800,
+            ),
+          ),
+          const SizedBox(height: 4),
+          Text(
+            'Aucun responsable rattaché — choisissez un foyer',
+            style: TextStyle(fontSize: 12, color: Colors.red.shade700),
+          ),
+          const SizedBox(height: 8),
+          _familyPlacementSection(),
+          const SizedBox(height: 16),
+        ],
         Text(
           _placementTitle,
           style: TextStyle(
@@ -1240,10 +1268,45 @@ class _AdminChildDetailModalState extends State<AdminChildDetailModal> {
       title: 'Choisir une famille',
     );
     if (selected == null || !mounted) return;
-    setState(() {
-      _selectedFamily = selected;
-      _dirty = true;
-    });
+
+    if (widget.isCreating) {
+      setState(() {
+        _selectedFamily = selected;
+        _dirty = true;
+      });
+      return;
+    }
+
+    // Édition orphelin (#157) : rattache immédiatement au foyer.
+    final enfantId = widget.enfant?.id;
+    if (enfantId == null || enfantId.isEmpty) return;
+
+    setState(() => _saving = true);
+    try {
+      for (final parentId in selected.parentUserIds) {
+        await UserService.attachEnfantToParent(
+          parentUserId: parentId,
+          enfantId: enfantId,
+        );
+      }
+      final refreshed = await UserService.getEnfant(enfantId);
+      if (!mounted) return;
+      setState(() {
+        _localParentLinks = refreshed.parentLinks;
+        _selectedFamily = selected;
+        _saving = false;
+      });
+      widget.onSaved?.call();
+      ScaffoldMessenger.of(context).showSnackBar(
+        const SnackBar(content: Text('Enfant rattaché au foyer')),
+      );
+    } catch (e) {
+      if (!mounted) return;
+      setState(() => _saving = false);
+      ScaffoldMessenger.of(context).showSnackBar(
+        SnackBar(content: Text(e.toString().replaceFirst('Exception: ', ''))),
+      );
+    }
   }
 
   Widget _familyPlacementSection() {