Integrations DI refactor, remove Sellasist/Baselinker, fix product-edit encoding (0.263)

- New: Domain\Integrations\IntegrationsRepository + admin\Controllers\IntegrationsController (DI)
- Cleanup: removed all Sellasist and Baselinker integrations from entire project
- Fix: product-edit.php Polish characters (UTF-8/CP1250 double-encoding)
- Update: factory\Integrations as facade (Apilo + ShopPRO only)
- Tests: 212 tests, 577 assertions

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

TESTING.md

@@ -52,11 +52,13 @@ tests/
 |   |   |-- Dictionaries/DictionariesRepositoryTest.php
 |   |   |-- Product/ProductRepositoryTest.php
 |   |   |-- Settings/SettingsRepositoryTest.php
-|   |   `-- User/UserRepositoryTest.php
+|   |   |-- User/UserRepositoryTest.php
+|   |   `-- Integrations/IntegrationsRepositoryTest.php
 |   `-- admin/
 |       `-- Controllers/
 |           |-- ArticlesControllerTest.php
 |           |-- DictionariesControllerTest.php
+|           |-- IntegrationsControllerTest.php
 |           |-- ProductArchiveControllerTest.php
 |           |-- SettingsControllerTest.php
 |           `-- UsersControllerTest.php
@@ -281,3 +283,17 @@ Nowe testy dodane 2026-02-13:
 
 Zaktualizowane testy 2026-02-13:
 - `tests/Unit/admin/Controllers/ArticlesControllerTest.php` (konstruktor z `Domain\\Pages\\PagesRepository`)
+
+## Aktualizacja suite (Integrations refactor, ver. 0.263)
+Ostatnio zweryfikowano: 2026-02-13
+
+```text
+OK (212 tests, 577 assertions)
+```
+
+Nowe testy dodane 2026-02-13:
+- `tests/Unit/Domain/Integrations/IntegrationsRepositoryTest.php` (16 testow: getSettings, getSetting, saveSetting, linkProduct, unlinkProduct, getProductSku, apiloGetAccessToken, invalid provider, settings table mapping)
+- `tests/Unit/admin/Controllers/IntegrationsControllerTest.php` (10 testow: kontrakty metod, return types, brak metod sellasist/baselinker)
+
+Zaktualizowane pliki:
+- `tests/bootstrap.php` (dodany stub `S::remove_special_chars()`)