Fix a11y icon, FAB label colors, add high-contrast stylesheet, sync theme vars

- Fix faIcon() to use <i> elements (FA7 compatibility)
- Fix #mokoThemeFab .label and button colors to white (visible on
  both light and dark themes)
- Fix font-weight typo (600px → 600)
- Add --footer-padding-* variables to all 6 theme files
- Create a11y-high-contrast.css with WCAG AAA contrast ratios for
  both light and dark modes
- Register high-contrast stylesheet in joomla.asset.json
- Lazy-load high-contrast CSS when a11y contrast toggle is activated

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/templates/dark.custom.css

@@ -813,6 +813,12 @@ color-scheme: dark;
 --table-active-color: var(--body-color);
 --table-active-bg: rgba(var(--white-rgb), 0.1);
 
+/* ===== FOOTER ===== */
+--footer-padding-top: 1rem;
+--footer-padding-bottom: 80px;
+--footer-grid-padding-y: 2.5rem;
+--footer-grid-padding-x: 0.5em;
+
 /* ===== BACKDROP ===== */
 --backdrop-zindex: 1040;
 --backdrop-bg: hsl(0, 0%, 0%);

src/templates/light.custom.css

@@ -812,6 +812,12 @@ color-scheme: light;
 --table-active-color: var(--body-color);
 --table-active-bg: rgba(var(--black-rgb), 0.075);
 
+/* ===== FOOTER ===== */
+--footer-padding-top: 1rem;
+--footer-padding-bottom: 80px;
+--footer-grid-padding-y: 2.5rem;
+--footer-grid-padding-x: 0.5em;
+
 /* ===== BACKDROP ===== */
 --backdrop-zindex: 1040;
 --backdrop-bg: hsl(0, 0%, 0%);