feat: advertise configured account heads during discovery

[Cryptoloveer]

Problem

Last-transaction discovery advertises only a random sample of account heads. Operators cannot ensure that locally important accounts are included in each discovery broadcast, so those accounts may take longer to be discovered by peers.

Fix

• Add atto.bootstrap.discovery.hinted-addresses as a local configuration property.
• Resolve all configured public keys to their current account-head transactions in one repository query.
• Include those heads alongside the existing random sample without changing the wire protocol.
• Ignore configured public keys that are not present locally.
• Deduplicate hinted heads that are already present in the random sample.

Validation

• Added a focused test covering a configured head alongside the random sample.
• The test verifies that a hinted head already in the random sample is emitted only once.
• Updated the existing unit-test fixture for the new configuration dependency.
• Addressed maintainer feedback by replacing per-address reads with one bulk query and removing the redundant algorithm check.
• Awaiting refreshed CI on the synchronized branch before marking the draft ready.

Reward address

atto://ad5mogtl3hfcherkbufxiewl7k74q7svljqdfgnby7d52lj4o2ifh2horqj6u

Closes #213.

[Cryptoloveer]

The focused implementation and duplicate-head test are now in place, and the branch is synchronized with current main. Could a maintainer approve the fork workflow run so I can confirm the full test suite before marking this ready?

[atto-reward-bot]

Thank you for your contribution! 🎉 This PR is eligible for an contribution-minor reward as a token of our appreciation. If you'd like to receive it, please add your address to the description of this PR. 🙏

[atto-reward-bot]

Thank you for your contribution! 🎉 This PR is eligible for an contribution-minor reward as a token of our appreciation and will be sent to atto://ad5mogtl3hfcherkbufxiewl7k74q7svljqdfgnby7d52lj4o2ifh2horqj6u once merged. Please note that rewards are not payments but our way of saying thank you. 🙏

[Cryptoloveer]

The requested bulk-read change is now pushed, the review thread has been addressed, and the branch is synchronized with current main. Could a maintainer approve the refreshed CI run? I’ll keep the PR in draft until it passes.