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/media/css/template.css

@@ -17070,8 +17070,8 @@ form .form-select {
 	background: var(--muted-color, #6d757e);
 	box-shadow: var(--box-shadow, 0 .5rem 1rem #00000066);
 	font: inherit;
-	color: var(--body-bg, #0e1318);
-	font-weight: 600px;
+	color: #fff;
+	font-weight: 600;
 }
 
 #mokoThemeFab.pos-br {
@@ -17133,10 +17133,11 @@ button#mokoThemeSwitch {
 #mokoThemeFab .label {
 	user-select: none;
 	font-size: .875rem;
+	color: #fff;
 }
 
 #mokoThemeFab button {
-	color: var(--body-bg, #0e1318);
+	color: #fff;
 }
 
 /* Auto toggle switch (on/off style) */