Add master dashboard reporter and settings UI

- New reporter module that pushes firm stats (total accounts, accounts
  traded, in trade) to a configurable master dashboard every 30 seconds
- Add Instance Name and Dashboard URL fields to the settings page
- Register master_dashboard_url and instance_name in settings API
- Seed default (empty) values for new settings in db

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

lib/db.ts

@@ -162,6 +162,8 @@ db.exec(`
 const seedSetting = db.prepare(`INSERT OR IGNORE INTO settings (key, value) VALUES (?, ?)`);
 seedSetting.run('max_concurrent_accounts', '5');
 seedSetting.run('tick_interval_seconds', '60');
+seedSetting.run('master_dashboard_url', '');
+seedSetting.run('instance_name', '');
 
 export function getSetting(key: string): string | null {
     const row = db.prepare('SELECT value FROM settings WHERE key = ?').get(key) as { value: string } | undefined;