Offline page redesign, remove brand showcase tab, force a11y/theme to bottom-right

- Offline page: full-viewport Joomla offline_image background, centered glass card
  overlay with logo glow, message, offline position, login accordion, copyright
- Favicon: added to offline page, HTML-escaped paths in helper
- Removed brand showcase tab, added footer CSS vars to CSS Variables tab
- Forced a11y toolbar and theme FAB to bottom-right (removed position selectors)

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

src/index.php

@@ -41,7 +41,7 @@ $params_favicon_source     = (string) $this->params->get('favicon_source', '');
 $params_theme_enabled      = $this->params->get('theme_enabled', 1);
 $params_theme_control_type = (string) $this->params->get('theme_control_type', 'radios');
 $params_theme_fab_enabled  = $this->params->get('theme_fab_enabled', 1);
-$params_theme_fab_pos      = $this->params->get('theme_fab_pos', 'br');
+$params_theme_fab_pos      = 'br';
 
 // Accessibility params
 $params_a11y_toolbar    = $this->params->get('a11y_toolbar_enabled', 1);
@@ -51,7 +51,7 @@ $params_a11y_contrast   = $this->params->get('a11y_high_contrast', 1);
 $params_a11y_links      = $this->params->get('a11y_highlight_links', 1);
 $params_a11y_font       = $this->params->get('a11y_readable_font', 1);
 $params_a11y_animations = $this->params->get('a11y_pause_animations', 1);
-$params_a11y_pos        = (string) $this->params->get('a11y_toolbar_pos', 'tl');
+$params_a11y_pos        = 'br';
 
 // Detecting Active Variables
 $option    = $input->getCmd('option', '');