ci: adopt immutable Node.js 24 Actions

[seoseo-ai]

Summary

• replace mutable GitHub Action tags with official Node.js 24 Action commits pinned to full immutable SHAs from jinwon-int/github-workflows/action-lock.json
• add weekly Dependabot updates for the github-actions ecosystem
• preserve existing triggers, matrices, commands, permissions, and application behavior

Public/private boundary

This repository is public while jinwon-int/github-workflows is private. GitHub does not resolve private cross-repository actions from public workflows, so this PR intentionally uses the approved official full SHAs directly instead of private central composite wrappers.

Validation

• central schema-aware Action audit: violations 0
• remaining mutable remote Action refs: 0
• actionlint: no findings
• git diff --check: clean
• previous failed run was isolated to Unable to resolve action jinwon-int/github-workflows, not found before any project command executed

Safety

• workflow/configuration source only
• no release, deployment, provider send, secret, permission, or data mutation
• Dependabot keeps the immutable public pins current through reviewed PRs

Related to jinwon-int/github-workflows#1.

[jinon86]

Reviewed seoseo-authored final commit ae58a75. New upstream run 29071357110 passed Node 20/22/24 with zero annotations; immutable Action audit and actionlint are clean.