Add server ownership, team access, role-based UI, and default admin role

- New migration 002_server_access.sql: created_by column + server_user table
- Server model: ownership, permission checks, team management methods
- Routes: /team routes, RoleMiddleware on /servers/create and /admin
- ServerController: permission checks via server_user, team CRUD methods
- TerminalController: server access checks
- DashboardController: filter servers by accessible ones
- ApiController: server access checks
- Views: team.php, team_server.php, sidebar Team link, hide actions by role
- Default user role changed from operator to admin on registration
- Admin user form defaults to admin role

src/Controllers/DashboardController.php

@@ -5,6 +5,7 @@ declare(strict_types=1);
 namespace ServerManager\Controllers;
 
 use ServerManager\Core\App;
+use ServerManager\Core\Session;
 use ServerManager\Models\Server;
 use ServerManager\Services\MonitoringService;
 use ServerManager\Services\AuditService;
@@ -28,7 +29,13 @@ class DashboardController
         $recentActivity = $this->auditService->getRecentActivity(10);
 
         $serverModel = new Server();
+        $userId = (int) Session::get('user_id');
+        $accessibleIds = $serverModel->getAccessibleServerIds($userId);
         $servers = $serverModel->findAll(true);
+        $servers = array_filter($servers, function ($s) use ($accessibleIds) {
+            return in_array((int) $s['id'], $accessibleIds, true);
+        });
+        $servers = array_values($servers);
 
         $this->view->display('dashboard.index', [
             'title' => 'Dashboard - ServerManager',