Bulk CDK: add GHA cron to bump CDK version in certified connectors (#66826)
## What
Part of
https://github.com/airbytehq/airbyte-internal-issues/issues/14308.
Example run
https://github.com/airbytehq/airbyte/actions/runs/18284850032, example
PR https://github.com/airbytehq/airbyte/pull/67093/. See also
https://github.com/airbytehq/airbyte-enterprise/pull/257.
The cron runs on the first Monday of every month. Past discussions
wanted every 3 weeks, but that's a PITA to do in GHA.
I added one more commit after that run:
679081a47d.
Just changing the trigger to be on a cron, and marking the PR as ready
for review.
There's no automation on actually merging the PRs, but they'll tag the
appropriate team(s) for review. In principle, reviewers can just click
the merge button on green CI though.
There's some weird behavior where the PR sometimes fails to submit b/c
of push protection rules
([example](https://github.com/airbytehq/airbyte/actions/runs/18235269794/job/51927690655#step:12:119)).
@wennergr is looking into this.
## How
Use the various gradle tasks we've added to upgrade the CDK version.
I wanted to use the [bump-version
command](https://github.com/airbytehq/airbyte/actions/workflows/bump-version-command.yml)
to do the metadata+changelog, but it seems to be
[broken](https://airbytehq-team.slack.com/archives/C02U9R3AF37/p1759499392004199).
Got claude to write a hacky equivalent.
(a lot of the bash stuff is also from claude, but heavily edited for
readability+comments+style. I've done enough testing to be confident in
it though.)
## Can this PR be safely reverted and rolled back?
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* If unsure, leave it blank.
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- [x] YES 💚
- [ ] NO ❌
6dbd718fed