Improve accessibility and add site quality CI

[daniel-techAI]

What changed

• fixes the five homepage business-category labels that failed WCAG AA contrast (3.99:1 → 6.39:1)
• adds a visible keyboard skip link with a focusable main-content target
• makes the mobile menu name reflect open/closed state and supports Escape with focus return
• labels navigation landmarks, converts labelled visual groups to explicit list/group semantics, and makes text input types explicit
• adds HTML validation plus Playwright/axe checks for every public HTML page, local links/assets, desktop, mobile, skip-link behavior, and mobile-menu keyboard behavior
• documents the local quality workflow

Why

The homepage’s category labels used a muted color below the 4.5:1 WCAG AA threshold, and keyboard users had no direct way to bypass the repeated header. The repository also lacked an automated regression gate for markup, links, and accessibility.

Impact

The existing static architecture and GitHub Pages URLs are unchanged. The current live Pages site remains available; these changes only take effect after review and merge.

Validation

• npm run check
  • HTML validation: passed
  • Playwright: 6 passed, 2 intentionally skipped by project scope
  • axe-core: no automated WCAG A/AA violations across all 13 public HTML routes
  • desktop and Pixel 7 mobile projects covered
• git diff --check: passed
• https://daniel-techai.github.io/Locriva/: HTTP 200 with the expected title before this PR

Manual follow-up

Automated checks reduce regressions but do not replace a manual screen-reader pass or usability testing with disabled users.