feat(127): polkurier integration foundation

Single-instance globalna konfiguracja polkurier.pl jako alternatywa
dla Apaczki: szyfrowany login + Token API, karta w hubie integracji
i realny test polaczenia przez apimetod=test_auth_api zweryfikowany
na zywym koncie operatora (Autoryzacja: 1).

ShipmentProviderRegistry netkniety - PolkurierShipmentService/
TrackingService w kolejnych fazach.

Kluczowe ustalenia kontraktu API (z SDK polkurier-sdk):
- POST https://api.polkurier.pl/ (jeden endpoint)
- JSON body: {authorization:{login,token}, apimetod, data}
- Sukces: top-level status === 'success' (nie 'ok')
- Blad: tresc w polu 'response' envelope'a
- Content-Type: application/json (strict, bez charset suffix)

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

database/migrations/20260514_000114_create_polkurier_integration_settings.sql

@@ -0,0 +1,29 @@
+CREATE TABLE IF NOT EXISTS `polkurier_integration_settings` (
+    `id` TINYINT UNSIGNED NOT NULL PRIMARY KEY,
+    `integration_id` INT UNSIGNED NULL,
+    `login` VARCHAR(190) NULL,
+    `api_token_encrypted` TEXT NULL,
+    `default_label_format` VARCHAR(8) NOT NULL DEFAULT 'PDF',
+    `created_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    `updated_at` DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+    UNIQUE KEY `polkurier_integration_settings_integration_unique` (`integration_id`),
+    CONSTRAINT `polkurier_integration_settings_integration_fk`
+        FOREIGN KEY (`integration_id`) REFERENCES `integrations` (`id`)
+        ON DELETE CASCADE ON UPDATE CASCADE
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;
+
+INSERT INTO `integrations` (`type`, `name`, `base_url`, `timeout_seconds`, `is_active`, `created_at`, `updated_at`)
+VALUES ('polkurier', 'polkurier', 'https://api.polkurier.pl/', 15, 1, NOW(), NOW())
+ON DUPLICATE KEY UPDATE
+    `base_url` = VALUES(`base_url`),
+    `timeout_seconds` = VALUES(`timeout_seconds`),
+    `updated_at` = VALUES(`updated_at`);
+
+INSERT INTO `polkurier_integration_settings` (`id`, `integration_id`, `created_at`, `updated_at`)
+SELECT 1, `id`, NOW(), NOW()
+FROM `integrations`
+WHERE `type` = 'polkurier' AND `name` = 'polkurier'
+LIMIT 1
+ON DUPLICATE KEY UPDATE
+    `integration_id` = VALUES(`integration_id`),
+    `updated_at` = VALUES(`updated_at`);