Soft-delete users instead of hard-deleting, add last login tracking

Fixes the 500 on admin user deletion: deleting a user with an
email_log row (i.e. basically anyone who received any email) hit an
unhandled ForeignKeyConstraintViolationException, since email_log,
reset_password_request and player all have non-nullable FKs to user
with no cascade at the DB level.

Instead of cascading the delete (which would be fine for email_log
and reset_password_request but risky for player - removing a player
row could corrupt other real players' session state), admin delete
now sets a deletedAt timestamp instead of removing the row:
- UserChecker blocks login for deleted users (checkPreAuth).
- EmailLoggerListener rejects the message before send for deleted
  recipients (checked at actual send time, not at queue time).
- Added a last_login_at column + a LoginSuccessEvent listener to
  populate it, and surfaced both last login and status in the admin
  users list.

Added `app:users:purge-deleted`, a command intended to run on a
schedule that permanently removes users who were soft-deleted more
than 3 months ago and never played a game (join to Player via a
NOT EXISTS subquery). For that eventual hard-delete to actually
succeed, email_log and reset_password_request now cascade-delete at
the DB level (migration drops+recreates both FK constraints with ON
DELETE CASCADE) - player intentionally still isn't cascaded, so a
user with game history can never be purged this way even by mistake.

src/Command/PurgeDeletedUsersCommand.php

@@ -0,0 +1,41 @@
+<?php
+declare(strict_types=1);
+
+namespace App\Command;
+
+use App\Tech\Repository\UserRepository;
+use Doctrine\ORM\EntityManagerInterface;
+use Symfony\Component\Console\Attribute\AsCommand;
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\OutputInterface;
+
+#[AsCommand(
+    name: 'app:users:purge-deleted',
+    description: 'Permanently removes soft-deleted users who never played a game, 3 months after deletion.'
+)]
+final class PurgeDeletedUsersCommand extends Command
+{
+    public function __construct(
+        private readonly UserRepository $userRepository,
+        private readonly EntityManagerInterface $entityManager,
+    ) {
+        parent::__construct();
+    }
+
+    protected function execute(InputInterface $input, OutputInterface $output): int
+    {
+        $deletedBefore = new \DateTimeImmutable('-3 months');
+        $users = $this->userRepository->findPurgeableDeletedUsers($deletedBefore);
+
+        foreach ($users as $user) {
+            $this->entityManager->remove($user);
+        }
+
+        $this->entityManager->flush();
+
+        $output->writeln(sprintf('<info>Purged %d deleted user(s).</info>', count($users)));
+
+        return Command::SUCCESS;
+    }
+}