fix(ci): use setup-python to avoid 504 errors and use project oxlint config

[lyzno1]

Fixes #29612

Summary

Use actions/setup-python before setup-uv in autofix.yml to provide Python from GitHub's official cache, avoiding intermittent 504 errors when uv tries to download python-build-standalone.

Screenshots

N/A - CI workflow change

Checklist

• [ ] This change requires a documentation update, included: Dify Document
• [x] I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• [x] I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• [x] I've updated the documentation accordingly.
• [x] I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

[gemini-code-assist[bot]]

[!NOTE] Gemini is unable to generate a summary for this pull request due to the file types involved not being currently supported.

[lyzno1]

Additional fix: oxlint config

Problem: CI used pnpx oxlint --fix without project config, causing inconsistent lint behavior between CI and local.

Fix: Changed to pnpm exec oxlint --config .oxlintrc.json --fix . to match local lint:oxlint script in package.json.

Commit	Description
c728ea4c49	Initial fix - missing pnpm exec
1d9059e576	Added pnpm exec to run project oxlint