Improved web landing page of LiveBridge

[syedarhamraza]

Summary

This PR upgrades the LiveBridge landing page (docs/index.html) to improve the overall landing page

Problem / motivation

-No Mobile navigation
-Old design language

Linked issue or discussion

Fixes #

Scope of changes

• docs/index.html:
  • Added SEO and OpenGraph metadata tags.
  • Implemented design tokens for brand teal colors, and typography weights (Plus Jakarta Sans, Inter).
  • Re-designed feature ticks to use circular SVG checkmark badges with proper line-alignment offsets.
  • Refactored the footer structure.
  • Wrapped release titles inside dynamic anchor links pointing to GitHub release pages when the API responds.
  • Implemented .btn:active click scale feedback for touch screen devices.
• docs/DESIGN_LANGUAGE.md made with gemini 3.5(f):
  • Created a developer design language specification sheet mapping color tokens, typography hierarchies, container rules, and viewport drawer behaviors

Screenshots / recordings

Testing

• I ran the relevant checks locally.
• I tested the affected flow manually.
• I included screenshots/recordings for UI changes.
• I documented any testing gaps below.

Testing notes:
Verified responsive layouts on emulated viewports down to 320px.
Confirmed menu visibility and scroll lock during collapsed address bar states on two different mobile Chrome.

Risk / compatibility

Contributor checklist

• This PR has one focused purpose (or a group of purposes).
• This PR does not include unrelated formatting, cleanup, or rewrites.
• I removed debug logs, local paths, temporary code, and unused dependencies.
• I updated localization strings for user-facing text. (if applicable)
• I updated documentation or issue templates if behavior changed.
• I reviewed every line, including AI-assisted/written code, and can explain it.
• I am ready to adjust the PR based on review instead of opening a replacement PR.