feat(icons): add the FA5 catalog, REST endpoint and unified icon helpers

Mirror the reference theme's universal picker on FA5: a generated full
catalog of the bundled FA5 Free 5.15.4 fonts (src/Icons/fa5-icons.php,
generated from the shipped CSS + SVG fonts), a zibsvg group parsed from
the runtime sprite so it cannot drift, and GET /aksrt/v1/icons/catalog.

Shared admin pieces: aksrt_icon_markup()/aksrt_sanitize_icon_value()
with an SVG allowlist, the picker field/modal assets, and one canonical
aksrt-font-awesome handle registered through aksrt_enqueue_fontawesome().

src/Admin/Admin.php

@@ -111,11 +111,16 @@ class Admin {
         }
 
         // Use the same local FA5 pack as the public stack.
-        wp_enqueue_style(
-            'aksrt-font-awesome',
-            get_template_directory_uri() . '/assets/fontawesome5/css/all.min.css',
-            [],
-            '5.15.4'
+        aksrt_enqueue_fontawesome();
+
+        // Frontend SVG sprite (defines window.aksrt_svgs and injects the symbol
+        // sheet) so schema icon fields can preview built-in zibsvg values.
+        wp_enqueue_script(
+            'aksrt-svg-sprite',
+            get_template_directory_uri() . '/assets/js/runtime/svg-icon.js',
+            ['jquery'],
+            (string) filemtime(get_template_directory() . '/assets/js/runtime/svg-icon.js'),
+            true
         );
 
         wp_enqueue_script(
@@ -186,6 +191,7 @@ class Admin {
             CommentController::class,
             MessageController::class,
             AIController::class,
+            \AKSRT\Icons\IconController::class,
         ];
 
         foreach ($controllers as $class_name) {

src/Core/ScriptsPart1b.php

@@ -25,17 +25,12 @@ trait ScriptsPart1b {
 			[],
 			'3.4.1'
 		);
-		wp_enqueue_style(
-			'fontawesome5',
-			$base_uri . '/assets/fontawesome5/css/all.min.css',
-			['bootstrap'],
-			'5.15.4'
-		);
+		aksrt_enqueue_fontawesome(['bootstrap']);
 		$main_css_path = get_template_directory() . '/assets/css/main.min.css';
 		wp_enqueue_style(
 			'aksrt-main',
 			$base_uri . '/assets/css/main.min.css',
-			['fontawesome5'],
+			['aksrt-font-awesome'],
 			file_exists($main_css_path) ? (string) filemtime($main_css_path) : $version
 		);
         wp_enqueue_style(

src/Icons/IconCatalog.php

@@ -0,0 +1,66 @@
+<?php
+/**
+ * @package AKSRT
+ */
+
+namespace AKSRT\Icons;
+
+defined('ABSPATH') || exit;
+
+/**
+ * Icon catalog for the universal icon picker.
+ *
+ * Two families:
+ *  - Font Awesome 5 Free (bundled, 5.15.4): static generated data in fa5-icons.php.
+ *  - Theme built-in SVG sprite: keys parsed from assets/js/runtime/svg-icon.js
+ *    (aksrt_svgs['key'] = '<path ...>') so the picker can never drift from the
+ *    frontend sprite. Parsed per file mtime and cached.
+ */
+final class IconCatalog {
+
+	/**
+	 * @return array<int, array{id:string,title:string,type:string,icons:string[]}>
+	 */
+	public static function groups(): array {
+		$fa = include AKSRT_DIR . '/src/Icons/fa5-icons.php';
+		if (!is_array($fa)) {
+			$fa = ['fas' => [], 'far' => [], 'fab' => []];
+		}
+
+		return [
+			['id' => 'fas', 'title' => __('FA 实色', 'aksrt'), 'type' => 'fa', 'icons' => array_values((array) ($fa['fas'] ?? []))],
+			['id' => 'far', 'title' => __('FA 常规', 'aksrt'), 'type' => 'fa', 'icons' => array_values((array) ($fa['far'] ?? []))],
+			['id' => 'fab', 'title' => __('FA 品牌', 'aksrt'), 'type' => 'fa', 'icons' => array_values((array) ($fa['fab'] ?? []))],
+			['id' => 'zibsvg', 'title' => __('主题内置 SVG', 'aksrt'), 'type' => 'svg', 'icons' => self::sprite_keys()],
+			['id' => 'custom', 'title' => __('自定义 SVG', 'aksrt'), 'type' => 'custom', 'icons' => []],
+		];
+	}
+
+	/**
+	 * Sprite symbol keys, e.g. ['like', 'view', ...] — derived from the
+	 * frontend sprite file, cached until the file changes.
+	 *
+	 * @return string[]
+	 */
+	public static function sprite_keys(): array {
+		$file = AKSRT_DIR . '/assets/js/runtime/svg-icon.js';
+		if (!is_readable($file)) {
+			return [];
+		}
+
+		$mtime = (string) filemtime($file);
+		$cache = get_transient('aksrt_sprite_keys_v1');
+		if (is_array($cache) && ($cache['mtime'] ?? '') === $mtime && isset($cache['keys'])) {
+			return array_values((array) $cache['keys']);
+		}
+
+		$src  = (string) file_get_contents($file);
+		$keys = [];
+		if (preg_match_all("/aksrt_svgs\\['([A-Za-z0-9_]+)'\\]\\s*=/", $src, $m)) {
+			$keys = array_values(array_unique($m[1]));
+		}
+
+		set_transient('aksrt_sprite_keys_v1', ['mtime' => $mtime, 'keys' => $keys], MONTH_IN_SECONDS);
+		return $keys;
+	}
+}

src/Icons/IconController.php

@@ -0,0 +1,37 @@
+<?php
+/**
+ * @package AKSRT
+ */
+
+namespace AKSRT\Icons;
+
+use AKSRT\Admin\ControllerBase;
+
+defined('ABSPATH') || exit;
+
+/**
+ * REST endpoint serving the icon picker catalog.
+ */
+class IconController extends ControllerBase {
+
+	private static $instance = null;
+
+	public static function get_instance(): self {
+		if (null === self::$instance) self::$instance = new self();
+		return self::$instance;
+	}
+
+	public function register_routes(): void {
+		register_rest_route(self::API_NAMESPACE, '/icons/catalog', [
+			'methods'             => 'GET',
+			'callback'            => [$this, 'get_catalog'],
+			'permission_callback' => [$this, 'check_permission'],
+		]);
+	}
+
+	public function get_catalog(): \WP_REST_Response {
+		return $this->success([
+			'groups' => IconCatalog::groups(),
+		]);
+	}
+}