Improve Upsert support for check-ins

### Problem Statement

Upserts are currently only available when manually using `Sentry.captureCheckIn()`

### Solution Brainstorm

- A new param for `CheckInUtils.withCheckIn()`
- Check if there's a `@Scheduled` annotation on a task annotated with `@SentryCheckIn` and read schedule from there
- Read schedule from `Trigger` in quartz
- CRON expressions in quartz have a different syntax we'd need to support

Start by reading CheckInUtils.withCheckIn() and the existing Sentry.captureCheckIn() path to understand current upsert handling. Compare the @SentryCheckIn, @Scheduled, and Quartz Trigger entry points, then define how supported schedules and CRON syntax should be handled; done means scheduled check-ins can use upserts consistently.

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