Fix remaining homepage label contrast

[daniel-techAI]

Summary

• darken the shared brass token used by small labels on white surfaces
• raise the affected labels above the WCAG AA 4.5:1 threshold
• add a deterministic contrast-ratio assertion for process and pricing labels

Validation

• all 13 public routes scanned at desktop and Pixel 7 sizes
• axe WCAG A/AA scan: zero violations
• no document-level horizontal overflow
• repository integrity script: 13 HTML files and 211 local references passed
• git diff --check passed