Add read-tracking and soft-delete to contact messages

Admin can now open a message via a per-row "View" page (which stamps
read_at the first time it's opened), see a sortable Read column on the
list instead of the raw message text, and soft-delete messages via a
Delete button on both the list and detail view. Deleted messages are
excluded from the default list so it doesn't pile up over time.

migrations/Version20260829130000.php

@@ -0,0 +1,26 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DoctrineMigrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+final class Version20260829130000 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return 'Add read_at to contact_message so admin can track which messages have been read';
+    }
+
+    public function up(Schema $schema): void
+    {
+        $this->addSql('ALTER TABLE contact_message ADD read_at DATETIME DEFAULT NULL');
+    }
+
+    public function down(Schema $schema): void
+    {
+        $this->addSql('ALTER TABLE contact_message DROP read_at');
+    }
+}