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.

resources/views/auth/login.php

@@ -6,11 +6,11 @@
   </header>
 
   <?php if (!empty($errorMessage)): ?>
-    <div class="alert-error" role="alert">
+    <div class="alert alert--danger login-alert" role="alert">
       <?= $e($errorMessage) ?>
     </div>
   <?php else: ?>
-    <div class="alert-error alert-error-placeholder" aria-hidden="true">
+    <div class="alert alert--danger login-alert login-alert-placeholder" aria-hidden="true">
       <?= $e($t('auth.login.error_placeholder')) ?>
     </div>
   <?php endif; ?>
@@ -22,6 +22,7 @@
       <span class="field-label"><?= $e($t('auth.login.email_label')) ?></span>
       <input
         type="email"
+        class="form-control"
         name="email"
         autocomplete="email"
         required
@@ -34,6 +35,7 @@
       <span class="field-label"><?= $e($t('auth.login.password_label')) ?></span>
       <input
         type="password"
+        class="form-control"
         name="password"
         autocomplete="current-password"
         required
@@ -41,6 +43,6 @@
       >
     </label>
 
-    <button type="submit" class="submit-btn"><?= $e($t('actions.login')) ?></button>
+    <button type="submit" class="btn btn--primary btn--block login-submit"><?= $e($t('actions.login')) ?></button>
   </form>
 </section>