feat(01-01): register custom post type for form submissions

- Created Umzugsliste_CPT class with singleton pattern
- Registered umzugsliste_entry post type
- German labels (Einträge, Eintrag)
- Settings: public=false, show_ui=true, show_in_menu=false
- Supports title field only (custom fields in Phase 6)
- Registered on init hook

includes/class-cpt.php

@@ -0,0 +1,71 @@
+<?php
+/**
+ * Custom Post Type Registration
+ */
+
+// Exit if accessed directly
+if ( ! defined( 'ABSPATH' ) ) {
+	exit;
+}
+
+/**
+ * CPT registration class
+ */
+class Umzugsliste_CPT {
+
+	/**
+	 * Single instance
+	 */
+	private static $instance = null;
+
+	/**
+	 * Get instance
+	 */
+	public static function get_instance() {
+		if ( null === self::$instance ) {
+			self::$instance = new self();
+		}
+		return self::$instance;
+	}
+
+	/**
+	 * Constructor
+	 */
+	private function __construct() {
+		add_action( 'init', array( $this, 'register_post_type' ) );
+	}
+
+	/**
+	 * Register the custom post type
+	 */
+	public function register_post_type() {
+		$labels = array(
+			'name'                  => 'Einträge',
+			'singular_name'         => 'Eintrag',
+			'menu_name'             => 'Einträge',
+			'name_admin_bar'        => 'Eintrag',
+			'add_new'               => 'Neu hinzufügen',
+			'add_new_item'          => 'Neuen Eintrag hinzufügen',
+			'new_item'              => 'Neuer Eintrag',
+			'edit_item'             => 'Eintrag bearbeiten',
+			'view_item'             => 'Eintrag ansehen',
+			'all_items'             => 'Alle Einträge',
+			'search_items'          => 'Einträge durchsuchen',
+			'not_found'             => 'Keine Einträge gefunden',
+			'not_found_in_trash'    => 'Keine Einträge im Papierkorb gefunden',
+		);
+
+		$args = array(
+			'labels'             => $labels,
+			'public'             => false,
+			'show_ui'            => true,
+			'show_in_menu'       => false,
+			'capability_type'    => 'post',
+			'supports'           => array( 'title' ),
+			'has_archive'        => false,
+			'rewrite'            => false,
+		);
+
+		register_post_type( 'umzugsliste_entry', $args );
+	}
+}