Use KREW bot identity for translation automation

[Jwaminju]

What changed

• Generate every new translation post with author: KREW.
• Attribute translation creation, review repair, feedback, and SEO metadata commits to Hugging Face KREW Translation Bot.
• Document that KREW_BOT_TOKEN must be owned by the huggingfacekrew GitHub account because GitHub uses the token owner as the PR and comment author.
• Add a regression assertion for the generated author front matter.

Why

Translation PRs and automation comments should be represented by the shared KREW bot account instead of an individual maintainer. Generated blog posts should also consistently resolve to the KREW author profile.

Deployment requirement

After merge, replace the KREW_BOT_TOKEN Actions secret in Hugging-Face-KREW/hf-workflow with a fine-grained token created by huggingfacekrew. Code changes alone cannot change the GitHub API author; the token owner determines that identity.

Validation

• 138 passed
• Workflow YAML files parse successfully.
• git diff --check passes.