Agregar estructura completa del tema APUS con Bootstrap 5 y optimizaciones de rendimiento

Se implementa tema WordPress personalizado para Análisis de Precios Unitarios con funcionalidades avanzadas:
- Sistema de templates (front-page, single, archive, page, 404, search)
- Integración de Bootstrap 5.3.8 con estructura modular de assets
- Panel de opciones del tema con Customizer API
- Optimizaciones de rendimiento (Critical CSS, Image Optimization, Performance)
- Funcionalidades SEO y compatibilidad con Rank Math
- Sistema de posts relacionados y tabla de contenidos
- Badge de categorías y manejo de AdSense diferido
- Tipografías Google Fonts configurables
- Documentación completa del tema y guías de uso

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

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

wp-content/themes/apus-theme/404.php

@@ -0,0 +1,123 @@
+<?php
+/**
+ * The template for displaying 404 pages (Not Found)
+ *
+ * This template displays a user-friendly error page when the requested
+ * content is not found, with helpful navigation options.
+ *
+ * @link https://developer.wordpress.org/themes/basics/template-hierarchy/#404-not-found
+ *
+ * @package Apus_Theme
+ * @since 1.0.0
+ */
+
+get_header();
+?>
+
+	<main id="main-content" class="site-main" role="main">
+
+		<div class="content-wrapper">
+
+			<section class="error-404 not-found" aria-labelledby="error-404-title">
+
+				<!-- Error Header -->
+				<header class="page-header">
+					<h1 id="error-404-title" class="page-title">
+						<?php esc_html_e( '404 - Page Not Found', 'apus-theme' ); ?>
+					</h1>
+				</header><!-- .page-header -->
+
+				<!-- Error Content -->
+				<div class="page-content">
+
+					<p class="error-message">
+						<?php esc_html_e( 'Oops! The page you are looking for might have been removed, had its name changed, or is temporarily unavailable.', 'apus-theme' ); ?>
+					</p>
+
+					<!-- Helpful Actions -->
+					<div class="error-actions">
+
+						<h2><?php esc_html_e( 'What can you do?', 'apus-theme' ); ?></h2>
+
+						<ul class="error-suggestions" role="list">
+							<li>
+								<a href="<?php echo esc_url( home_url( '/' ) ); ?>">
+									<?php esc_html_e( 'Go to the homepage', 'apus-theme' ); ?>
+								</a>
+							</li>
+							<li>
+								<?php esc_html_e( 'Check the URL for typos', 'apus-theme' ); ?>
+							</li>
+							<li>
+								<?php esc_html_e( 'Use the navigation menu above', 'apus-theme' ); ?>
+							</li>
+						</ul>
+
+						<!-- Recent Posts -->
+						<?php
+						$recent_posts = wp_get_recent_posts(
+							array(
+								'numberposts' => 5,
+								'post_status' => 'publish',
+							)
+						);
+
+						if ( ! empty( $recent_posts ) ) :
+							?>
+							<div class="recent-posts-section">
+								<h3><?php esc_html_e( 'Recent Posts', 'apus-theme' ); ?></h3>
+								<ul class="recent-posts-list" role="list">
+									<?php foreach ( $recent_posts as $recent ) : ?>
+										<li>
+											<a href="<?php echo esc_url( get_permalink( $recent['ID'] ) ); ?>">
+												<?php echo esc_html( $recent['post_title'] ); ?>
+											</a>
+										</li>
+									<?php endforeach; ?>
+								</ul>
+							</div>
+							<?php
+							wp_reset_postdata();
+						endif;
+						?>
+
+						<!-- Categories -->
+						<?php
+						$categories = get_categories(
+							array(
+								'orderby'    => 'count',
+								'order'      => 'DESC',
+								'number'     => 5,
+								'hide_empty' => true,
+							)
+						);
+
+						if ( ! empty( $categories ) ) :
+							?>
+							<div class="categories-section">
+								<h3><?php esc_html_e( 'Browse by Category', 'apus-theme' ); ?></h3>
+								<ul class="categories-list" role="list">
+									<?php foreach ( $categories as $category ) : ?>
+										<li>
+											<a href="<?php echo esc_url( get_category_link( $category->term_id ) ); ?>">
+												<?php echo esc_html( $category->name ); ?>
+												<span class="category-count">(<?php echo esc_html( $category->count ); ?>)</span>
+											</a>
+										</li>
+									<?php endforeach; ?>
+								</ul>
+							</div>
+						<?php endif; ?>
+
+					</div><!-- .error-actions -->
+
+				</div><!-- .page-content -->
+
+			</section><!-- .error-404 -->
+
+		</div><!-- .content-wrapper -->
+
+	</main><!-- #main-content -->
+
+<?php
+get_footer();