feat: configure UTM links, use CDN for fonts, align Home styling

[grabbou]

Note

Adds automatic UTM params to Callstack external links, switches Alliance font to CDN, updates CTA copy/links, and refines homepage/footer layout and paddings.

• Plugin/Config:
  • Update CTA defaults: new copy and https://www.callstack.com/contact links.
  • Add UTM_CAMPAIGN/UTM_MEDIUM constants and expose via builderConfig.
  • Normalize options now supports $TITLE replacement in CTA URLs.
• Components:
  • Button: auto-append UTM params to callstack.com external links using site title and location; new location prop.
  • Pass location to CTAs in HomeBanner, OutlineCTA, and DocFooterCTA.
• Styles/UI:
  • Load Alliance No. 2 via CDN in global styles; remove tester font-face file.
  • Rework home/footer visuals: new footer background assets, opacity fixes, and layout adjustments; unify paddings/radii.
  • Tweak home hero/banner wrappers, margins, and spacing.
• Docs:
  • README updates: clarify Alliance font usage and switch guidance to overriding header font via CSS variable.

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[grabbou]

In the future, we should also improve README (currently points to plugin, not preset).

[jbroma]

LGTM 🎉