Enhance admin dashboard and team management features

- Added a quick admin link section in the admin dashboard for managing team cards.
- Updated the admin licenses template to correct German language spelling.
- Improved the appointments template with conditional rendering for test package options.
- Enhanced the base template with a logo image and adjusted brand styling.
- Updated the license management template for consistent German language usage.
- Removed the tutorial template and replaced it with a new admin team management template.
- Introduced a new admin team management page allowing for the addition, editing, and deletion of team members.

Website/templates/admin_licenses.html

@@ -19,7 +19,7 @@
             {% endfor %}
         </select>
         <input type="text" name="school_name" placeholder="Schulname" required>
-        <input type="text" name="license_key" placeholder="Lizenz-Key (optional, eigener Wert moeglich)">
+        <input type="text" name="license_key" placeholder="Lizenz-Key (optional, eigener Wert möglich)">
         <input type="text" name="plan" placeholder="Plan (z. B. Standard)">
         <input type="text" name="status" placeholder="Status (Aktiv, Pausiert)">
         <input type="text" name="valid_until" placeholder="Gültig bis (YYYY-MM-DD)">