feat: WC-native logging + Add to phpList button on order page

Logging:
- Replace custom file logger with wc_get_logger() (source: woolist-phplist)
- Logs now appear in WooCommerce → Status → Logs, no filesystem access needed
- Remove log viewer / Clear Log from settings page (WC UI handles this)
- Keep "Enable debug logging" checkbox to control DEBUG-level verbosity

Order page meta box:
- New "phpList Sync" side meta box on every order edit page
- Works with both classic (shop_order) and HPOS (woocommerce_page_wc-orders)
- Shows billing email + dropdown of all configured lists
- "Add to phpList" button triggers AJAX subscribe, shows inline result
- Result and full API trace logged to WC logs under woolist-phplist source
- woolist-admin.js handles button state and response display

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

woolist-phplist/includes/class-woolist-logger.php

@@ -1,14 +1,13 @@
 <?php
 /**
- * Simple file-based logger for WooList.
+ * Logger for WooList — delegates to WooCommerce's built-in logging system.
  *
- * Writes to wp-content/uploads/woolist-logs/woolist.log.
- * The directory is protected from direct HTTP access via .htaccess.
+ * Logs are visible at WooCommerce → Status → Logs, source: woolist-phplist.
  *
  * Levels:
  *   INFO  — always written (subscription events, connection test results)
  *   ERROR — always written (API failures, config problems)
- *   DEBUG — written only when "Enable debug logging" is on (full request/response)
+ *   DEBUG — written only when "Enable debug logging" is checked in settings
  *
  * @package WooList
  */
@@ -17,38 +16,19 @@ defined( 'ABSPATH' ) || exit;
 
 class WooList_Logger {
 
-	/** Absolute path to the log file. */
-	private static string $log_file = '';
+	private const SOURCE = 'woolist-phplist';
 
 	/** Whether verbose debug lines are recorded. */
 	private static bool $debug_enabled = false;
 
-	/** Maximum log file size in bytes before rotation (1 MB). */
-	private const MAX_SIZE = 1048576;
+	/** Lazy-loaded WC_Logger instance. */
+	private static ?WC_Logger_Interface $wc_logger = null;
 
 	/**
-	 * Initialise the logger: create the log directory and read the debug setting.
-	 * Must be called after WordPress options are available.
+	 * Initialise: read the debug setting.
+	 * Called on plugins_loaded after options are available.
 	 */
 	public static function init(): void {
-		$upload     = wp_upload_dir();
-		$log_dir    = $upload['basedir'] . '/woolist-logs';
-
-		if ( ! is_dir( $log_dir ) ) {
-			wp_mkdir_p( $log_dir );
-		}
-
-		// Block direct HTTP access and directory listing.
-		$htaccess = $log_dir . '/.htaccess';
-		if ( ! file_exists( $htaccess ) ) {
-			file_put_contents( $htaccess, "Require all denied\ndeny from all\n" );
-		}
-		$index = $log_dir . '/index.php';
-		if ( ! file_exists( $index ) ) {
-			file_put_contents( $index, "<?php // Silence is golden.\n" );
-		}
-
-		self::$log_file      = $log_dir . '/woolist.log';
 		self::$debug_enabled = ( get_option( 'woolist_enable_debug_log' ) === 'yes' );
 	}
 
@@ -56,22 +36,21 @@ class WooList_Logger {
 
 	/** Always logged. Use for normal subscription / connection events. */
 	public static function info( string $message ): void {
-		self::write( 'INFO', $message );
+		self::wc()->info( $message, [ 'source' => self::SOURCE ] );
 	}
 
-	/** Always logged. Also echoes to php error_log as a fallback. */
+	/** Always logged. */
 	public static function error( string $message ): void {
-		self::write( 'ERROR', $message );
-		error_log( '[WooList ERROR] ' . $message );
+		self::wc()->error( $message, [ 'source' => self::SOURCE ] );
 	}
 
 	/**
 	 * Logged only when debug mode is enabled.
-	 * Use for full request URLs, raw response bodies, step-by-step flow.
+	 * Use for full request URLs (password redacted), raw responses, flow steps.
 	 */
 	public static function debug( string $message ): void {
 		if ( self::$debug_enabled ) {
-			self::write( 'DEBUG', $message );
+			self::wc()->debug( $message, [ 'source' => self::SOURCE ] );
 		}
 	}
 
@@ -87,55 +66,17 @@ class WooList_Logger {
 		return preg_replace( '/(\bpassword=)[^&]+/', '$1***', $url );
 	}
 
-	/**
-	 * Return the last $lines lines of the log as a string.
-	 *
-	 * @param int $lines Number of lines to return.
-	 * @return string Log tail, or an empty string when the log doesn't exist yet.
-	 */
-	public static function read_recent( int $lines = 300 ): string {
-		if ( empty( self::$log_file ) || ! file_exists( self::$log_file ) ) {
-			return '';
-		}
-
-		$content = file_get_contents( self::$log_file );
-		if ( $content === false || $content === '' ) {
-			return '';
-		}
-
-		$all    = explode( "\n", rtrim( $content ) );
-		$recent = array_slice( $all, -$lines );
-		return implode( "\n", $recent );
-	}
-
-	/** Truncate the log file without deleting it. */
-	public static function clear(): void {
-		if ( ! empty( self::$log_file ) ) {
-			file_put_contents( self::$log_file, '' );
-		}
-	}
-
-	public static function get_log_path(): string {
-		return self::$log_file;
-	}
-
 	public static function is_debug_enabled(): bool {
 		return self::$debug_enabled;
 	}
 
 	// ── Internal ─────────────────────────────────────────────────────────────
 
-	private static function write( string $level, string $message ): void {
-		if ( empty( self::$log_file ) ) {
-			return;
+	/** Return (and lazy-load) the WC_Logger instance. */
+	private static function wc(): WC_Logger_Interface {
+		if ( self::$wc_logger === null ) {
+			self::$wc_logger = wc_get_logger();
 		}
-
-		// Rotate if the file exceeds MAX_SIZE.
-		if ( file_exists( self::$log_file ) && filesize( self::$log_file ) >= self::MAX_SIZE ) {
-			rename( self::$log_file, self::$log_file . '.old' );
-		}
-
-		$line = '[' . gmdate( 'Y-m-d H:i:s' ) . ' UTC] [' . $level . '] ' . $message . "\n";
-		file_put_contents( self::$log_file, $line, FILE_APPEND | LOCK_EX );
+		return self::$wc_logger;
 	}
 }