Fix TOC Sidebar: Agregar variables CSS faltantes del template y cambiar a fuente Poppins

Problema:
- TOC sidebar usaba system fonts en lugar de Poppins
- Faltaban variables CSS del template (--color-navy-primary, --color-neutral-*)
- Variables de color estaban intercambiadas (#495057 vs #6c757d)

Solución:
1. Agregar variables faltantes a variables.css:
   - --color-navy-primary: #1e3a5f
   - --color-navy-light: #2c5282
   - --color-neutral-50: #f8f9fa
   - --color-neutral-100: #e9ecef
   - --color-neutral-600: #495057 (text default)
   - --color-neutral-700: #6c757d (text secondary)
   - --color-orange-light: #FFB800
   - --color-orange-hover: #FF6B35

2. Cambiar --font-family-base de system fonts a 'Poppins', sans-serif
   (Google Fonts Poppins ya se carga en enqueue-scripts.php)

3. Incrementar APUS_VERSION de 1.0.2 a 1.0.3 para cache busting

Archivos modificados:
- wp-content/themes/apus-theme/assets/css/variables.css
- wp-content/themes/apus-theme/functions.php

Reabre issue #121

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

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

wp-content/themes/apus-theme/functions.php

@@ -14,7 +14,7 @@ if (!defined('ABSPATH')) {
 /**
  * Theme Version
  */
-define('APUS_VERSION', '1.0.2');
+define('APUS_VERSION', '1.0.3');
 
 /**
  * Theme Setup