Add contact form with reCAPTCHA, saved to DB, viewable in admin

Adds a public /contact page (name/email/message, protected by the same
reCAPTCHA v3 setup used on registration) that persists submissions to
a new contact_message table, plus a Contact section in the admin panel
to read them. Linked from the site footer.

templates/website/contact.html.twig

@@ -0,0 +1,31 @@
+{% extends 'layout/site.html.twig' %}
+
+{% block title %}Contact | {{ 'site.name'|trans }}{% endblock %}
+
+{% block body %}
+<div class="row justify-content-center">
+    <div class="col-lg-7">
+        <div class="text-center mb-4">
+            <h1 class="display-6 fw-bold">Contact</h1>
+            <p class="lead text-secondary">Got a question, a bug to report, or just want to say hi?</p>
+        </div>
+
+        <div class="card shadow-sm">
+            <div class="card-body">
+                {{ form_errors(contactForm) }}
+
+                {{ form_start(contactForm) }}
+                    {{ form_row(contactForm.name) }}
+                    {{ form_row(contactForm.email) }}
+                    {{ form_row(contactForm.message) }}
+                    {{ form_row(contactForm.captcha) }}
+
+                    <div class="d-grid mt-3">
+                        <button type="submit" class="btn btn-primary">Send Message</button>
+                    </div>
+                {{ form_end(contactForm) }}
+            </div>
+        </div>
+    </div>
+</div>
+{% endblock %}