refactor(inc, image-optimizer): restructure /inc architecture and standardize image optimizer module

- reorganized /inc directory structure for improved separation of concerns
  - grouped files into customizer, utilities, and tools
  - improved naming consistency across files (e.g. *-settings, template-tags, etc.)
  - simplified functions.php includes for better readability and maintainability

- refactored Customizer structure
  - extracted image optimizer settings from core-settings into dedicated module
  - consolidated settings, UI logic, and styles into a single feature file
  - improved naming consistency for hooks and functions

- standardized Image Optimizer admin tool
  - renamed "Performance Tools" to "Image Optimizer" across UI and hooks
  - updated admin page registration, callback names, and menu labels
  - aligned AJAX nonce naming for consistency and clarity

- preserved all existing logic and behavior (no functional changes)
- improved overall code organization and long-term maintainability

no breaking changes

inc/customizer/social-settings.php

@@ -0,0 +1,97 @@
+<?php
+/**
+ * Social Links Customizer Options
+ *
+ * @package zeitfresser
+ */
+
+if ( ! function_exists( 'zeitfresser_get_social_links' ) ) {
+    function zeitfresser_get_social_links() {
+        return array(
+            'facebook'  => esc_html__( 'Facebook', 'zeitfresser' ),
+            'instagram' => esc_html__( 'Instagram', 'zeitfresser' ),
+            'youtube'   => esc_html__( 'YouTube', 'zeitfresser' ),
+            'linkedin'  => esc_html__( 'LinkedIn', 'zeitfresser' ),
+            'twitter'   => esc_html__( 'Twitter', 'zeitfresser' ),
+            'pinterest' => esc_html__( 'Pinterest', 'zeitfresser' ),
+            'tiktok'    => esc_html__( 'TikTok', 'zeitfresser' ),
+            'mastodon'  => esc_html__( 'Mastodon', 'zeitfresser' ),
+            'github'    => esc_html__( 'GitHub', 'zeitfresser' ),
+            'matrix'    => esc_html__( 'Matrix.org', 'zeitfresser' ),
+        );
+    }
+}
+
+add_action( 'customize_register', 'zeitfresser_social_links' );
+
+function zeitfresser_social_links( $wp_customize ) {
+
+    /**
+     * 🔥 Heading Control (falls noch nicht vorhanden)
+     */
+    if ( class_exists( 'WP_Customize_Control' ) && ! class_exists( 'ZTFR_Customize_Heading_Control' ) ) {
+        class ZTFR_Customize_Heading_Control extends WP_Customize_Control {
+            public $type = 'ztfr-heading';
+
+            public function render_content() {
+                ?>
+                <span style="display:block; font-weight:600; font-size:14px; margin:15px 0 5px;">
+                    <?php echo esc_html( $this->label ); ?>
+                </span>
+                <?php
+            }
+        }
+    }
+
+    /**
+     * ------------------------
+     * SOCIAL HEADING
+     * ------------------------
+     */
+    $wp_customize->add_setting(
+        'ztfr_social_heading',
+        array(
+            'sanitize_callback' => 'sanitize_text_field',
+        )
+    );
+
+    $wp_customize->add_control(
+        new ZTFR_Customize_Heading_Control(
+            $wp_customize,
+            'ztfr_social_heading',
+            array(
+                'label'    => esc_html__( 'Social Links', 'zeitfresser' ),
+                'section'  => 'ztfr_general',
+                'priority' => 30,
+            )
+        )
+    );
+
+    /**
+     * Social URLs
+     */
+    $social_links = zeitfresser_get_social_links();
+
+    $priority = 31;
+
+    foreach ( $social_links as $key => $label ) {
+
+        $wp_customize->add_setting(
+            'social_links_' . $key,
+            array(
+                'default'           => '',
+                'sanitize_callback' => 'esc_url_raw',
+            )
+        );
+
+        $wp_customize->add_control(
+            'social_links_' . $key,
+            array(
+                'type'     => 'url',
+                'section'  => 'ztfr_general',
+                'label'    => $label,
+                'priority' => $priority++,
+            )
+        );
+    }
+}