Leantime has HTML injection through firstname and lastname fields

Summary

### Summary Leantime v2.3.27 is vulnerable to Stored HTML Injection. The `firstname` and `lastname` fields in the admin user edit page are rendered without HTML escaping, allowing an authenticated user to inject arbitrary HTML that executes when the profile is viewed.

### Vulnerable File `app/Domain/Users/Templates/editUser.tpl.php`

### Vulnerable Code (Lines ~14-17) ```php value="<?php echo $values['firstname'] ?>" value="<?php echo $values['lastname'] ?>" ``` These fields output raw user input without sanitization.

### Steps to Reproduce 1. Login as admin > Go to Settings > Users > Edit any user 2. Enter HTML payload in First Name or Last Name field: `<h1>INJECTED</h1>` 3. Save the user profile 4. Create or view an article — the injected HTML renders in the author name

### Fix Replace unescaped `echo` with `htmlspecialchars()`: ```php value="<?php echo htmlspecialchars($values['firstname'], ENT_QUOTES, 'UTF-8') ?>" value="<?php echo htmlspecialchars($values['lastname'], ENT_QUOTES, 'UTF-8') ?>" ``` Or use the existing `$this->e()` helper already used in `editOwn.tpl.php`.

### Impact - Stored HTML injection visible to all users viewing affected content - Can be used for phishing, fake login forms, and UI defacement - Affects all versions before 3.3.0