feat: Implement user authentication and database migration system

- Refactored AuthService to use UserRepository for user authentication.
- Added .env file for environment configuration.
- Created migration system with Migrator and ConnectionFactory classes.
- Added database migration files for creating users table.
- Implemented settings controller for managing database migrations.
- Developed user repository for user data handling.
- Created users controller for user management interface.
- Added frontend standards and migration documentation.
- Introduced reusable UI components and jQuery alerts module.

DOCS/FRONTEND_STANDARDS.md

@@ -0,0 +1,17 @@
+# Frontend Standards
+
+## 1) Wspolne style UI
+- Powtarzalne elementy (np. przyciski, tabele, paginacja, alerty, pola formularzy) trzymamy w:
+  - `resources/scss/shared/_ui-components.scss`
+- Widoki maja korzystac z klas wspolnych (`btn`, `table`, `pagination`, `form-control`, `alert`) zamiast duplikowania stylu lokalnie.
+
+## 2) Moduly JS wielokrotnego uzycia
+- Kazdy modul przenoszalny trzymamy w oddzielnym folderze:
+  - `resources/modules/<module-name>/`
+- Minimalny zestaw plikow:
+  - `resources/modules/<module-name>/<module-name>.js`
+  - `resources/modules/<module-name>/<module-name>.scss`
+- Modul ma byc niezalezny od logiki projektu (brak hardcoded sciezek i zaleznosci biznesowych).
+
+## 3) Przyklad
+- Referencyjny modul: `resources/modules/jquery-alerts/`