Standardize empty/loading states and improve a11y in dashboard UI

[mhbdev]

What is this PR about?

• Replace text-only loading/empty states with shadcn Empty + Skeleton across dashboard, settings, and data list views.
• Add shared ListSkeleton helper to keep loading layouts consistent and reduce layout shift.
• Improve accessibility for interactive UI (social icon links and password visibility toggles).

Changes

• New reusable ListSkeleton in list-skeleton.tsx.
• Standardized empty/loading patterns in dashboard pages (monitoring, servers, deployments, schedules, backups, domains, requests, etc.).
• Updated disabled preview deployments messaging to use Empty with CTA.
• Fixed nested interactive elements + added aria labels in onboarding layout.
• Improved password toggle button focus/aria in input component.

Checklist

Before submitting this PR, please make sure that:

• You created a dedicated branch based on the canary branch.
• You have read the suggestions in the CONTRIBUTING.md file https://github.com/Dokploy/dokploy/blob/canary/CONTRIBUTING.md#pull-request
• You have tested this PR in your local instance.

Issues related (if applicable)

closes #3513