feat(#131): fiches parent/AM éditable, placement AM↔enfant, statuts garde/sans_garde

Squash merge develop → master.

- Fiche parent éditable (co-parent, PATCH fiche, GET /parents)
- Fiche AM 3 onglets (PATCH fiche, rattacher/détacher enfants)
- Table enfants_assistantes_maternelles + enum garde/sans_garde
- Migration SQL + BDD.sql canonique
- Correctifs recette : @Get() parents, DTO fiche AM, fix NIR

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

frontend/lib/utils/am_vigilance.dart

@@ -0,0 +1,45 @@
+import 'package:p_tits_pas/models/assistante_maternelle_model.dart';
+
+/// Places disponibles attendues : capacité max − enfants rattachés.
+int? amExpectedPlacesAvailable({
+  required int? maxChildren,
+  required int childrenCount,
+}) {
+  if (maxChildren == null) return null;
+  return (maxChildren - childrenCount).clamp(0, maxChildren);
+}
+
+/// True si la valeur déclarée par l'AM ne correspond pas au calcul métier.
+bool amHasPlacesInconsistency({
+  required int? maxChildren,
+  required int? placesAvailable,
+  required int childrenCount,
+}) {
+  final expected = amExpectedPlacesAvailable(
+    maxChildren: maxChildren,
+    childrenCount: childrenCount,
+  );
+  if (expected == null) return false;
+  if (placesAvailable == null) return childrenCount > (maxChildren ?? 0);
+  return placesAvailable != expected;
+}
+
+String? amPlacesVigilanceMessage(AssistanteMaternelleModel am) {
+  if (!amHasPlacesInconsistency(
+    maxChildren: am.maxChildren,
+    placesAvailable: am.placesAvailable,
+    childrenCount: am.children.length,
+  )) {
+    return null;
+  }
+  final stored = am.placesAvailable;
+  final expected = amExpectedPlacesAvailable(
+    maxChildren: am.maxChildren,
+    childrenCount: am.children.length,
+  );
+  final storedLabel = stored?.toString() ?? 'non renseigné';
+  final expectedLabel = expected?.toString() ?? '–';
+  return 'Point de vigilance : l\'AM déclare $storedLabel place(s) disponible(s), '
+      'alors que capacité ${am.maxChildren ?? '–'} − '
+      '${am.children.length} enfant(s) rattaché(s) = $expectedLabel.';
+}