feat(05-admin-panel): Admin panel z historią rezerwacji

Phase 5 complete — CPT carei_reservation z automatycznym zapisem,
lista z kolumnami i filtrem statusu, meta box szczegółów,
system statusów nowe/przeczytane/zrealizowane, auto-mark-read.

Milestone v0.1 Formularz Rezerwacji MVP — all 5 phases complete.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

wp-content/plugins/carei-reservation/carei-reservation.php

@@ -50,6 +50,7 @@ function carei_parse_env() {
  */
 require_once CAREI_RESERVATION_PATH . 'includes/class-softra-api.php';
 require_once CAREI_RESERVATION_PATH . 'includes/class-rest-proxy.php';
+require_once CAREI_RESERVATION_PATH . 'includes/class-admin-panel.php';
 
 /**
  * Initialize plugin on plugins_loaded
@@ -73,6 +74,9 @@ add_action( 'plugins_loaded', function () {
 
     // Initialize REST proxy
     new Carei_REST_Proxy();
+
+    // Initialize admin panel
+    new Carei_Admin_Panel();
 } );
 
 /**