[CrazyBoy49z]

Refine the error content while preserving the real Lazy Admin shell.

• Remove the redundant nested card header and oversized bordered container.
• Create a clear hierarchy with a large HTTP status, icon, descriptive copy and actions.
• Match the admin's primary color and keep existing Lazy UI buttons.
• Use small scoped fallback styles for the illustration/typography so package upgrades work without rebuilding host Tailwind assets.
• Keep the 500/503 standalone fallback unchanged and public error pages untouched.

One commit. CI and authenticated visual verification pending.