Fork PR creation is blocked for prepared #9236 docs fix

Issue Summary

A docs fix for #9236 is prepared and pushed, but GitHub currently blocks opening a pull request from Lan's public fork with:

GraphQL: xuezhaolan does not have the correct permissions to execute `CreatePullRequest` (createPullRequest)

Prepared branch: https://github.com/xuezhaolan/formbricks/tree/fix/docker-authzed-bootstrap-link

Commit: https://github.com/xuezhaolan/formbricks/commit/9f8baa18fc9d49e8a96b80b8921838fed75d46cd

What the branch changes

• Replaces the 404ing stable/docker/authzed-postgres-bootstrap.sh URL in docs/self-hosting/setup/docker.mdx.
• Uses the same pinned helper commit and checksum already used by docker/formbricks.sh.
• Fails closed if checksum verification fails, with sha256sum and shasum -a 256 support.

Verification

• Confirmed current docs helper URL returns 404.
• Confirmed pinned helper downloads successfully.
• Verified checksum matches 70975701cdf0dcffef5d3573a7514360e87428bb07cc4bfb4dbf47ae0c2e93a5.
• Verified the copied shell block downloads, verifies, and chmods the helper.
• Ran pnpm exec prettier --check docs/self-hosting/setup/docker.mdx successfully.

Next step

If maintainers enable fork PR creation or invite Lan as a contributor, I can open this as a normal PR immediately. Until then, the branch above is ready for review/cherry-pick.