fix(accessibility): Update colors for WCAG AA contrast compliance

Phase 4.4 PageSpeed Accessibility fixes:
- cta-box-sidebar: title/description colors from white to navy-dark (#0E2337)
- contact-form: info_value_color from #D5D8DA to #495057, button text to navy-dark
- cta-lets-talk: text_color from white to navy-dark
- css-tablas-apu: .c3 column color from #6c757d to #495057 (7.0:1 ratio)

All changes ensure minimum 4.5:1 contrast ratio for normal text (WCAG AA).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Schemas/cta-lets-talk.json

@@ -154,9 +154,9 @@
         "text_color": {
           "type": "color",
           "label": "Color del texto",
-          "default": "#FFFFFF",
+          "default": "#0E2337",
           "editable": true,
-          "description": "Color del texto y del ícono del botón"
+          "description": "Fase 4.4 Accesibilidad: navy-dark para contraste WCAG AA (4.8:1) sobre fondo naranja"
         },
         "text_hover_color": {
           "type": "color",