Add Stripe Connect account support and account.updated webhook handler

- Add stripeChargesEnabled and stripePayoutsEnabled fields to User entity + migration
- Handle account.updated webhook: sync charges_enabled and payouts_enabled from Stripe
- Add createAccountConnect() and createAccountLink() to StripeService
- Update organizer approved email with Stripe verification notice
- Tests: webhook account.updated with flags, unknown account, User stripe fields

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

migrations/Version20260319194243.php

@@ -0,0 +1,33 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DoctrineMigrations;
+
+use Doctrine\DBAL\Schema\Schema;
+use Doctrine\Migrations\AbstractMigration;
+
+/**
+ * Auto-generated Migration: Please modify to your needs!
+ */
+final class Version20260319194243 extends AbstractMigration
+{
+    public function getDescription(): string
+    {
+        return '';
+    }
+
+    public function up(Schema $schema): void
+    {
+        // this up() migration is auto-generated, please modify it to your needs
+        $this->addSql('ALTER TABLE "user" ADD stripe_charges_enabled BOOLEAN NOT NULL DEFAULT FALSE');
+        $this->addSql('ALTER TABLE "user" ADD stripe_payouts_enabled BOOLEAN NOT NULL DEFAULT FALSE');
+    }
+
+    public function down(Schema $schema): void
+    {
+        // this down() migration is auto-generated, please modify it to your needs
+        $this->addSql('ALTER TABLE "user" DROP stripe_charges_enabled');
+        $this->addSql('ALTER TABLE "user" DROP stripe_payouts_enabled');
+    }
+}