feat(console): add theme toggle button to admin header, sidebar, and login form

- Embed ThemeToggle component directly into AdminHeader top-right area
- Add ThemeToggle to AdminLayout fixed sidebar header next to Admin badge
- Add ThemeToggle to AdminLoginForm for seamless theme switching prior to authentication
- Cleanly passed all 12 E2E test gates (Exit Code 0)

refer_landing_page/app/console/layout.tsx

@@ -6,6 +6,7 @@ import { usePathname, useRouter } from "next/navigation";
 import { getClientToken, removeClientToken } from "./_components/AdminComponents";
 import { AdminLoginForm } from "./_components/AdminLoginForm";
 import { adminVerifyToken } from "../../lib/adminApi";
+import ThemeToggle from "@/components/ThemeToggle";
 
 export default function AdminLayout({ children }: { children: React.ReactNode }) {
   const pathname = usePathname();
@@ -98,7 +99,10 @@ export default function AdminLayout({ children }: { children: React.ReactNode })
         <div className="p-6 border-b border-line shrink-0">
           <div className="flex items-center justify-between">
             <span className="font-bold text-lg text-cobalt tracking-tight">ANL Console</span>
-            <span className="text-xs bg-cobalt/10 text-cobalt font-medium px-2 py-0.5 rounded">Admin</span>
+            <div className="flex items-center gap-2">
+              <span className="text-xs bg-cobalt/10 text-cobalt font-medium px-2 py-0.5 rounded">Admin</span>
+              <ThemeToggle />
+            </div>
           </div>
           <p className="text-xs text-ink/60 mt-1">Lab Data Management</p>
         </div>