Add meal v2 flow and user timezone support

Introduces a new add_meal_v2 blueprint with barcode scanning, item search, and improved meal logging UI. Adds user timezone support: login form now captures timezone, User model and database schema updated, and timezone is set on login. Refactors templates and forms to support these changes, and removes the old login template.

application/auth/templates/login.html

@@ -3,7 +3,10 @@
 {% block content %}
 <div class="container d-flex justify-content-center align-items-center">
     <div class="card shadow-sm p-4" style="width: 100%; max-width: 400px;">
-        <h3 class="mb-4 text-center">Login</h3>
+        <h3 class="mb-1 text-center">Login</h3>
+        <p class="text-center text-muted small mb-4">
+            Your timezone will be saved to show times correctly.
+        </p>
         <form method="post">
             {{ form.hidden_tag() }}
 
@@ -27,10 +30,21 @@
                 {% endif %}
             </div>
 
+            {{ form.timezone(id="timezone") }}
+
             <div class="d-grid">
                 {{ form.submit(class="btn btn-primary btn-lg") }}
             </div>
         </form>
     </div>
 </div>
-{% endblock%}
+{% endblock %}
+
+{% block scripts %}
+<script>
+    document.addEventListener('DOMContentLoaded', () => {
+        const tzField = document.getElementById('timezone');
+        tzField.value = Intl.DateTimeFormat().resolvedOptions().timeZone;
+    });
+</script>
+{% endblock %}