feat: add Security room with Users and Groups sections

- Add Security room accessible from main navigation
- Implement Users list page with DataGrid (fetches from /auth/users)
- Implement Groups list page with DataGrid (fetches from /auth/groups)
- Move user/group management from Control Room to dedicated Security room
- Remove Authentik section from Control Room navigation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

lib/shared/layouts/app_scaffold.dart

@@ -1,6 +1,7 @@
 import 'package:flutter/material.dart';
 import 'package:go_router/go_router.dart';
 import 'package:tatlock_ui/features/control_room/router.dart';
+import 'package:tatlock_ui/features/security/router.dart';
 import 'package:tatlock_ui/routing/app_router.dart';
 import 'package:tatlock_ui/shared/layouts/widgets/top_header_bar.dart';
 
@@ -54,7 +55,8 @@ class AppScaffold extends StatelessWidget {
     final location = GoRouterState.of(context).matchedLocation;
 
     if (location.startsWith(ControlRoomRoutes.base)) return 1;
-    if (location.startsWith(AppRoutes.parlor)) return 2;
+    if (location.startsWith(SecurityRoutes.base)) return 2;
+    if (location.startsWith(AppRoutes.parlor)) return 3;
     // Settings is no longer in main nav (accessed via Profile dropdown)
     return 0; // Front Hall
   }
@@ -63,7 +65,8 @@ class AppScaffold extends StatelessWidget {
     final route = switch (index) {
       0 => AppRoutes.frontHall,
       1 => ControlRoomRoutes.containers,
-      2 => AppRoutes.parlor,
+      2 => SecurityRoutes.users,
+      3 => AppRoutes.parlor,
       _ => AppRoutes.frontHall,
     };
     context.go(route);

lib/shared/layouts/widgets/top_header_bar.dart

@@ -34,6 +34,11 @@ class TopHeaderBar extends StatelessWidget {
       selectedIcon: Icons.dns,
       label: 'Control Room',
     ),
+    _RoomDestination(
+      icon: Icons.security_outlined,
+      selectedIcon: Icons.security,
+      label: 'Security',
+    ),
     _RoomDestination(
       icon: Icons.lightbulb_outline,
       selectedIcon: Icons.lightbulb,