Add registration functionality and update authentication views

- Implemented a new method in AuthController to display the registration form with localized labels and session error handling.
- Updated the login view to include a link for account creation.
- Enhanced the registration view with a link to the login form.
- Removed the obsolete showRegisterPage view to streamline the codebase.

Views/Auth/login.phtml

@@ -28,6 +28,9 @@ include dirname(__DIR__).'/header.phtml';
                 </div>
                 <button class="login-btn" type="submit">Einloggen</button>
             </form>
+            <div style="text-align:center; margin-top: 1.5em;">
+                <a href="?controller=Auth&do=register" class="login-link">Konto erstellen</a>
+            </div>
         <?php endif; ?>
     </div>
 </div>

Views/Auth/register.phtml

@@ -58,4 +58,8 @@
         <button type="submit">Registrieren</button>
     </form>
 
+<div style="text-align:center; margin-top: 1.5em;">
+    <a href="?controller=Auth&do=showAuthForm" class="login-link">Bereits registriert? Hier einloggen</a>
+</div>
+
 <?php include dirname(__DIR__).'/footer.phtml'; ?>

Views/Auth/showAuthForm.phtml

@@ -17,7 +17,7 @@ include dirname(__DIR__) . '/header.phtml';
         </form>
         <button class="button-loggin">Login</button>
         <a class="link-passwort-vergessen">Passwort vergessen?</a>
-        <a class="link-konto-erstellen">Konto erstellen</a>
+        <a class="link-konto-erstellen" href="?controller=Auth&do=showRegistrationForm">Konto erstellen</a>
     </div>
 </div>
 

Views/Auth/showRegistrationForm.phtml

@@ -60,7 +60,8 @@ include dirname(__DIR__) . '/header.phtml';
             </label>
         </form>
         <button class="button-register">Registrieren</button>
-        <a class="link-konto-erstellen">Login</a>
+        <div style="text-align:center; margin-top: 1.5em;">
+        <a href="?controller=Auth&do=showAuthForm" class="login-link">Bereits registriert? Hier einloggen</a>
     </div>
 </div>
 <?php