* Fix Telegram notification spam with channel-level rate limiting
Addresses issue #950 where Telegram notifications were sent excessively
(96-288 messages per day per task) due to the delete-and-recreate pattern
added in commit 105a913a to fix navbar notification pile-up.
Changes:
- Add channel_sent_at JSON field to notifications table to track when
each channel (telegram, email, push) was last sent
- Add helper methods to notification model:
- markChannelAsSent(channel): Records send timestamp
- wasChannelRecentlySent(channel, threshold): Checks if sent within 24h
- Modify sendTelegramNotification() to check rate limit before sending
- Update service layer (dueTaskService, deferredTaskService,
dueProjectService) to preserve channel_sent_at when recreating
notifications
- Add comprehensive unit and integration tests (20 tests, all passing)
Impact:
- Reduces Telegram notifications from 96-288/day to 1/day per item
- Preserves in-app notification refresh behavior (every 5-15 min)
- Maintains navbar pile-up fix from original commit
- Rate limit configurable (default: 24 hours)
Fixes#950
* Fix linting and formatting issues
* Fix integration test that was trying to access private function
* Fix prettier formatting in integration test
11cd77bedd