feat: add theme toggle and animated background

[prashant2007-wq]

Summary

Adds a dark/light theme toggle to the dashboard and introduces a subtle animated background.

Fixes #40

What changed

• Added theme toggle button in the dashboard navbar
• Added light/dark theme CSS variable support
• Persisted selected theme using localStorage
• Added smooth theme transitions
• Added responsive animated gradient/orb background
• Added reduced-motion support for accessibility

Testing

Tested manually:

• Opened gateway/dashboard.html
• Switched between light and dark themes
• Refreshed the page and verified theme persistence
• Checked navbar, cards, tables, filters, buttons, modal, and side panel
• Verified animated background remains subtle and responsive

[vercel]

@prashant2007-wq is attempting to deploy a commit to the Vaibhav Sharma's projects Team on Vercel.

A member of the Team first needs to authorize it.

[prashant2007-wq]

Hi @sharmavaibhav31,

I checked the failed check details. It looks like the Vercel deployment is blocked because a member of the Vercel team needs to authorize the deployment from my fork.

The change is limited to gateway/dashboard.html, and I have manually tested the dashboard locally by opening the HTML file, switching between dark/light themes, refreshing to verify persistence, and checking the animated background.

Could you please authorize or re-run the Vercel deployment check when convenient?

[prashant2007-wq]

Hi @sharmavaibhav31,

I checked the failed check details. It looks like the Vercel deployment is blocked because a member of the Vercel team needs to authorize deployment from my fork.

I also tried cleaning gateway/dashboard.html locally for hidden Unicode/control characters, but git diff is empty and the working tree is clean, so there are no additional local changes to push from my side.

The change is limited to gateway/dashboard.html, and I manually tested:

• dark/light theme toggle
• theme persistence after refresh
• animated background
• dashboard UI visibility in both themes

Could you please authorize or re-run the Vercel deployment check when convenient?