feat: allow regular users to view their own tenant's org chart

Changes the /users endpoint to allow RoleUser access and securely restricts the returned data to only users within their affiliated tenants. Removes the unnecessary back button from the Org Chart view since it's now a top-level nav item.

adminfront/src/features/tenants/routes/TenantOrgChartPage.tsx

@@ -211,11 +211,6 @@ export function TenantOrgChartPage() {
     <div className="flex flex-col h-[calc(100vh-theme(spacing.32))] bg-slate-50 rounded-xl overflow-hidden shadow-sm border border-slate-200">
       <header className="flex items-center justify-between px-6 py-4 bg-white border-b border-slate-200 shadow-sm z-10 shrink-0">
         <div className="flex items-center gap-4">
-          <Button variant="outline" size="icon" asChild className="h-8 w-8">
-            <Link to="/tenants">
-              <ChevronLeft size={16} />
-            </Link>
-          </Button>
           <div>
             <h2 className="text-xl font-bold text-slate-800">조직도</h2>
             <p className="text-xs text-slate-500">