feat(inscription): email accusé réception, photos enfants, formulaires identité

- Backend: mail après inscription parent avec n° dossier, UPLOAD_PHOTOS_DIR, réponse API
- Frontend: imageBytes + payload photo, utils email/code postal/téléphone, champs dédiés
- Formulaires admin, login (focus), personal_info, child_card, custom_app_text_field

Made-with: Cursor

frontend/lib/widgets/admin/parametres_panel.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:go_router/go_router.dart';
 import 'package:p_tits_pas/services/configuration_service.dart';
+import 'package:p_tits_pas/utils/email_utils.dart';
 import 'package:p_tits_pas/widgets/admin/relais_management_panel.dart';
 
 /// Panneau Paramètres admin : Email (SMTP), Personnalisation, Avancé.
@@ -182,6 +183,9 @@ class _ParametresPanelState extends State<ParametresPanel> {
               hintText: 'admin@example.com',
             ),
             keyboardType: TextInputType.emailAddress,
+            autocorrect: false,
+            enableSuggestions: false,
+            inputFormatters: const [EmailMaxLengthFormatter()],
           ),
           actions: [
             TextButton(
@@ -191,7 +195,17 @@ class _ParametresPanelState extends State<ParametresPanel> {
             FilledButton(
               onPressed: () {
                 final t = c.text.trim();
-                if (t.isNotEmpty) Navigator.pop(ctx, t);
+                if (t.isEmpty) {
+                  return;
+                }
+                final err = validateEmail(t, allowEmpty: true);
+                if (err != null) {
+                  ScaffoldMessenger.of(ctx).showSnackBar(
+                    SnackBar(content: Text(err)),
+                  );
+                  return;
+                }
+                Navigator.pop(ctx, t);
               },
               child: const Text('Envoyer'),
             ),

frontend/lib/widgets/admin/relais_management_panel.dart

@@ -482,6 +482,9 @@ class _RelaisFormDialogState extends State<_RelaisFormDialog> {
     if (!_isValidPostalCode(_postalCodeCtrl.text.trim())) {
       return false;
     }
+    if (validateFrenchNationalPhone(_ligneFixeCtrl.text, allowEmpty: true) != null) {
+      return false;
+    }
 
     for (final day in _days) {
       final ferme = _closedByDay[day] ?? false;
@@ -721,11 +724,7 @@ class _RelaisFormDialogState extends State<_RelaisFormDialog> {
         TextField(
           controller: _ligneFixeCtrl,
           keyboardType: TextInputType.phone,
-          inputFormatters: [
-            FilteringTextInputFormatter.digitsOnly,
-            LengthLimitingTextInputFormatter(10),
-            FrenchPhoneNumberFormatter(),
-          ],
+          inputFormatters: frenchPhoneInputFormatters,
           decoration: const InputDecoration(
             labelText: 'Ligne fixe',
             hintText: '01 23 45 67 89',