Restore readable footer copyright text

Product: Shared 360TFT website
Priority: P1
Status: In Review
Process: /home/kevin/360tft-hub/docs/playbook/PRD-EXECUTION-SOP.md

Problem

The shared footer renders its 14px copyright line as #666666 on #111111, approximately 3.1:1 contrast. That misses the WCAG AA 4.5:1 requirement for normal text on every page using the default layout.

Expected Experience

Footer copyright text remains visually secondary while being comfortably readable on desktop and mobile and meeting WCAG AA contrast.

Honesty artifact

• Confirmed source values: --text-muted: #666666, --bg-card: #111111, --text-secondary: #B3B3B3, and .copyright uses the muted token.
• Contrast is calculated from those source tokens; production computed-style and axe verification remain required after deployment.
• The service-worker console defect is not part of this change. It was already independently fixed on main by commit e6157bc before this branch started.
• No claim is made that this repairs unrelated contrast issues elsewhere.

Scope

• Use the existing --text-secondary design token for the copyright line.
• Add a browser regression assertion for the computed colour.
• Do not change footer content, layout, navigation, page content or analytics.

Verification

• The token pair #B3B3B3 on #111111 measures at least 4.5:1.
• The Jekyll build succeeds.
• Desktop and mobile production browsers compute the copyright colour as rgb(179, 179, 179).
• Production accessibility scan reports no footer colour-contrast violation.