feat(01-01): create main plugin file with bootstrap code

- WordPress plugin header with proper metadata
- Plugin version constants and paths
- Main Umzugsliste class with singleton pattern
- Activation/deactivation hooks with flush_rewrite_rules
- Autoloader for includes/ directory
- Init hook to initialize plugin components

umzugsliste.php

@@ -0,0 +1,106 @@
+<?php
+/**
+ * Plugin Name: Umzugsliste
+ * Description: Email-basiertes Möbelauswahlsystem für Siegel Umzüge
+ * Version: 1.0.0
+ * Author: Siegel Umzüge
+ * Text Domain: umzugsliste
+ * Domain Path: /languages
+ */
+
+// Exit if accessed directly
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
+// Plugin version
+define( 'UMZUGSLISTE_VERSION', '1.0.0' );
+define( 'UMZUGSLISTE_PLUGIN_DIR', plugin_dir_path( __FILE__ ) );
+define( 'UMZUGSLISTE_PLUGIN_URL', plugin_dir_url( __FILE__ ) );
+
+/**
+ * Main plugin class
+ */
+class Umzugsliste {
+
+	/**
+	 * Single instance of the class
+	 */
+	private static $instance = null;
+
+	/**
+	 * Get single instance
+	 */
+	public static function get_instance() {
+		if ( null === self::$instance ) {
+			self::$instance = new self();
+		}
+		return self::$instance;
+	}
+
+	/**
+	 * Constructor
+	 */
+	private function __construct() {
+		$this->load_dependencies();
+		$this->init_hooks();
+	}
+
+	/**
+	 * Load required files
+	 */
+	private function load_dependencies() {
+		require_once UMZUGSLISTE_PLUGIN_DIR . 'includes/class-cpt.php';
+		require_once UMZUGSLISTE_PLUGIN_DIR . 'includes/class-admin-menu.php';
+	}
+
+	/**
+	 * Initialize WordPress hooks
+	 */
+	private function init_hooks() {
+		add_action( 'init', array( $this, 'init' ) );
+	}
+
+	/**
+	 * Initialize plugin components
+	 */
+	public function init() {
+		// Initialize CPT
+		Umzugsliste_CPT::get_instance();
+
+		// Initialize admin menu
+		if ( is_admin() ) {
+			Umzugsliste_Admin_Menu::get_instance();
+		}
+	}
+}
+
+/**
+ * Activation hook
+ */
+function umzugsliste_activate() {
+	// Initialize CPT to register post type
+	require_once UMZUGSLISTE_PLUGIN_DIR . 'includes/class-cpt.php';
+	Umzugsliste_CPT::get_instance();
+
+	// Flush rewrite rules
+	flush_rewrite_rules();
+}
+register_activation_hook( __FILE__, 'umzugsliste_activate' );
+
+/**
+ * Deactivation hook
+ */
+function umzugsliste_deactivate() {
+	// Flush rewrite rules
+	flush_rewrite_rules();
+}
+register_deactivation_hook( __FILE__, 'umzugsliste_deactivate' );
+
+/**
+ * Initialize plugin
+ */
+function umzugsliste_init() {
+	return Umzugsliste::get_instance();
+}
+add_action( 'plugins_loaded', 'umzugsliste_init' );