Route scheduled balance monitoring through QueueHandler

[TaprootFreak]

Summary

• processScheduledBalanceMonitoring() was calling processBalances() and processChannels() directly, bypassing the QueueHandler used by the webhook-triggered processBalanceMonitoring()
• This could cause race conditions when both cron and webhook paths run concurrently
• Now routes through processBalanceMonitoring(), which serializes all balance processing through the existing QueueHandler

Test plan

• yarn lint passes
• yarn build passes
• Verify cron still triggers every 5 minutes in dev/staging logs
• Confirm no duplicate or conflicting DB writes when webhook and cron overlap