Add new templates for user authentication and management

- Created `unlogged-layout.php` and `unlogged.php` for the login page layout.
- Implemented `main-view.php` for system update management with progress tracking.
- Added `user-2fa.php` for two-factor authentication verification.
- Developed `user-edit.php` for editing user details and privileges.
- Introduced `users-list.php` for displaying and managing user accounts.
- Added `.htaccess` configuration for URL rewriting and security settings.

admin/templates/html/panel.php

@@ -0,0 +1,8 @@
+<div class="panel <?= $this -> params['class'];?>">
+  <div class="panel-heading">
+    <span class="panel-title"><?= $this -> params['title'];?></span>
+  </div>
+  <div class="panel-body">
+    <?= $this -> params['content'];?>
+  </div>
+</div>