Replace old team system with work teams (equipos de trabajo)

- New migration 003_teams.sql: teams, team_user, team_server tables
- New Team model with CRUD, members, and server assignment
- New TeamController with full team management
- New views: teams/index, teams/create, teams/show
- Server model: getUserRole and getAccessibleServerIds now include team-based access
- Sidebar: Teams link under Administration (admin+ only)
- Routes: old /team routes removed, new /teams routes added
- Removed old ServerController team methods and views
- Fixed sidebar empty accessible IDs returning all servers
- Fixed dashboard and API to show empty when no accessible servers

src/Controllers/DashboardController.php

@@ -31,11 +31,9 @@ class DashboardController
         $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) {
+        $servers = !empty($accessibleIds) ? array_values(array_filter($serverModel->findAll(true), function ($s) use ($accessibleIds) {
             return in_array((int) $s['id'], $accessibleIds, true);
-        });
-        $servers = array_values($servers);
+        })) : [];
 
         $this->view->display('dashboard.index', [
             'title' => 'Dashboard - ServerManager',