feat: add global user administration for admin users

Backend:
- Add getAllUsuarios() to get users from all tenants
- Add updateUsuarioGlobal() to edit users and change their tenant
- Add deleteUsuarioGlobal() for global user deletion
- Add global admin check based on tenant RFC
- Add new API routes: /usuarios/global/*

Frontend:
- Add UserListItem.tenantId and tenantName fields
- Add /admin/usuarios page with full user management
- Support filtering by tenant and search
- Inline editing for name, role, and tenant assignment
- Group users by company for better organization
- Add "Admin Usuarios" menu item for admin navigation

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

packages/shared/src/types/user.ts

@@ -38,12 +38,15 @@ export interface UserListItem {
   active: boolean;
   lastLogin: string | null;
   createdAt: string;
+  tenantId?: string;
+  tenantName?: string;
 }
 
 export interface UserUpdate {
   nombre?: string;
   role?: 'admin' | 'contador' | 'visor';
   active?: boolean;
+  tenantId?: string;
 }
 
 export interface AuditLog {