feat(19-ui-integration): przycisk Drukuj, bulk print, kolejka wydruku

- Przycisk "Drukuj" w prepare.php i show.php z AJAX + duplikat protection
- Bulk print z listy zamówień (checkboxy + header action)
- Kolejka wydruku w Ustawienia > Drukowanie (filtr statusu, retry)
- POST /api/print/jobs/bulk endpoint (package_ids + order_ids)
- ensureLabel() auto-download przez ShipmentProviderRegistry
- Apaczka carrier_id = nazwa usługi, kolumna Przewoznik
- Tab persistence (localStorage), label file_exists check
- Fix use statement ApaczkaApiClient, redirect po utworzeniu przesyłki
- Phase 17 (receipt duplicate guard) + Phase 18 (print queue backend) docs

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

database/migrations/20260322_000058_create_print_tables.sql

@@ -0,0 +1,28 @@
+-- Print API keys for remote printing authentication
+CREATE TABLE IF NOT EXISTS print_api_keys (
+    id INT AUTO_INCREMENT PRIMARY KEY,
+    name VARCHAR(128) NOT NULL,
+    key_hash VARCHAR(128) NOT NULL,
+    key_prefix VARCHAR(8) NOT NULL,
+    is_active TINYINT(1) NOT NULL DEFAULT 1,
+    last_used_at DATETIME NULL,
+    created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    UNIQUE INDEX print_api_keys_hash_unique (key_hash),
+    INDEX print_api_keys_active_idx (is_active)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
+
+-- Print jobs queue for remote label printing
+-- No FK constraints: order_id/package_id types may vary across environments
+CREATE TABLE IF NOT EXISTS print_jobs (
+    id INT UNSIGNED AUTO_INCREMENT PRIMARY KEY,
+    order_id BIGINT UNSIGNED NOT NULL,
+    package_id BIGINT UNSIGNED NOT NULL,
+    label_path VARCHAR(255) NOT NULL,
+    status ENUM('pending', 'printing', 'completed', 'failed') NOT NULL DEFAULT 'pending',
+    created_by INT UNSIGNED NOT NULL,
+    created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    completed_at DATETIME NULL,
+    INDEX print_jobs_status_idx (status),
+    INDEX print_jobs_order_idx (order_id),
+    INDEX print_jobs_package_idx (package_id)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;