feat(#95): implémenter la gestion Relais admin et le rattachement gestionnaire

Ajoute la section Paramètres territoriaux avec CRUD Relais, modale de saisie structurée, états visuels harmonisés, et rattachement d'un relais principal aux gestionnaires via l'API.

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

frontend/lib/screens/administrateurs/admin_dashboardScreen.dart

@@ -19,6 +19,7 @@ class _AdminDashboardScreenState extends State<AdminDashboardScreen> {
   bool? _setupCompleted;
   int mainTabIndex = 0;
   int subIndex = 0;
+  int settingsSubIndex = 0;
 
   @override
   void initState() {
@@ -35,10 +36,12 @@ class _AdminDashboardScreenState extends State<AdminDashboardScreen> {
         if (!completed) mainTabIndex = 1;
       });
     } catch (e) {
-      if (mounted) setState(() {
-        _setupCompleted = false;
-        mainTabIndex = 1;
-      });
+      if (mounted) {
+        setState(() {
+          _setupCompleted = false;
+          mainTabIndex = 1;
+        });
+      }
     }
   }
 
@@ -54,6 +57,12 @@ class _AdminDashboardScreenState extends State<AdminDashboardScreen> {
     });
   }
 
+  void onSettingsSubTabChange(int index) {
+    setState(() {
+      settingsSubIndex = index;
+    });
+  }
+
   @override
   Widget build(BuildContext context) {
     if (_setupCompleted == null) {
@@ -83,6 +92,11 @@ class _AdminDashboardScreenState extends State<AdminDashboardScreen> {
             DashboardUserManagementSubBar(
               selectedSubIndex: subIndex,
               onSubTabChange: onSubTabChange,
+            )
+          else
+            DashboardSettingsSubBar(
+              selectedSubIndex: settingsSubIndex,
+              onSubTabChange: onSettingsSubTabChange,
             ),
           Expanded(
             child: _getBody(),
@@ -95,7 +109,10 @@ class _AdminDashboardScreenState extends State<AdminDashboardScreen> {
 
   Widget _getBody() {
     if (mainTabIndex == 1) {
-      return ParametresPanel(redirectToLoginAfterSave: !_setupCompleted!);
+      return ParametresPanel(
+        redirectToLoginAfterSave: !_setupCompleted!,
+        selectedSettingsTabIndex: settingsSubIndex,
+      );
     }
     switch (subIndex) {
       case 0: