Contact Announcement Frequency Doubles in Significant Update!

New changes slash announcement intervals from 30 to 15 minutes, ensuring users receive timely news like never before!

Commit Details:

chore: increase contact announcement interval (#2296) ## Why is this change needed? Reduces the interval from every 30 to every 15 minutes for announcement, with randomized start minute ## Merge Checklist _Choose all relevant options below by adding an `x` now or at any time before submitting for review_ - [x] PR title adheres to the [conventional commits](https://www.conventionalcommits.org/en/v1.0.0/) standard - [x] PR has a [changeset](https://github.com/farcasterxyz/hub-monorepo/blob/main/CONTRIBUTING.md#35-adding-changesets) - [x] PR has been tagged with a change label(s) (i.e. documentation, feature, bugfix, or chore) - [ ] PR includes [documentation](https://github.com/farcasterxyz/hub-monorepo/blob/main/CONTRIBUTING.md#32-writing-docs) if necessary. <!-- start pr-codex --> --- ## PR-Codex overview This PR adjusts the announcement interval for contact info in the `@farcaster/hubble` package. ### Detailed summary - Changed the random minute calculation from every 30 minutes to every 15 minutes in `hubble.ts` - Updated the cron syntax for `gossipContactInfoJobScheduler` to reflect the new interval > ✨ Ask PR-Codex anything about this PR by commenting with `/codex {your question}` <!-- end pr-codex -->