Create offline-installable release of harper-pro (LMDB + RocksDB binaries)

The old `HarperFast/harperdb` (4.x) repo includes an offline-release pipeline that pre-downloads all machine-specific binaries so the resulting tarball can be installed on any target machine without network access. We need the equivalent in `harper-pro`, with the additional twist of coordinating both LMDB and RocksDB native binaries.

## Reference

- 4.x version: [`utility/devops/build/all-in-one-build.sh#L50`](https://github.com/HarperFast/harperdb/blob/main/utility/devops/build/all-in-one-build.sh#L50) — pulls LMDB binaries per arch.

## Asks

- Build script in `harper-pro` that produces an offline-installable artifact.
- Pull and bundle `@harperfast/rocksdb-js` prebuilds in addition to LMDB.
- Cover the same target matrix as the 4.x offline release (or a documented subset).
- Wire into the existing release workflow (`create-release.yaml`, `publish-npm.yaml`, etc.) so an offline tarball is produced alongside the standard release.

## Acceptance criteria

- An offline tarball can be installed on a target machine with no network access and Harper starts cleanly.
- Both LMDB and RocksDB native modules are bundled per supported arch.
- Documented build/install procedure.

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Tracked in Jira: [CORE-3031](https://harperdb.atlassian.net/browse/CORE-3031)

🤖 Filed by Claude on behalf of Kris.