feat: extend notification system with batch sender, bulk dialog, and logging

Add NotificationLog schema extensions (nullable userId, email, roundId,
projectId, batchId fields), batch notification sender service, and bulk
notification dialog UI. Include utility scripts for debugging and seeding.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

scripts/test-db.cjs

@@ -0,0 +1,20 @@
+require('dotenv').config();
+const { PrismaClient } = require('@prisma/client');
+
+async function main() {
+  console.log('DATABASE_URL:', process.env.DATABASE_URL);
+  const p = new PrismaClient({ log: ['query', 'info', 'warn', 'error'] });
+  try {
+    const result = await p.$queryRawUnsafe('SELECT 1 as ok');
+    console.log('Connected!', result);
+  } catch (e) {
+    console.error('Error code:', e.code);
+    console.error('Error meta:', JSON.stringify(e.meta, null, 2));
+    console.error('Message:', e.message);
+  } finally {
+    await p.$disconnect();
+    process.exit(0);
+  }
+}
+
+main();