chore: finish the Guard-Core org migration (docs, metadata, links)

[rennf93]

Summary

Finishes the Guard-Core org migration for everything the workflow/OIDC pass (#27) did not cover: documentation, repo metadata, cross-references, and packaging URLs. History entries are intentionally preserved.

Categories of changes

• Docs site URLs: rennf93.github.io/djapi-guard -> guard-core.github.io/djapi-guard (path suffixes preserved) in README, mkdocs.yml (site_url, og:image), pyproject Documentation URL, issue template, SECURITY.md, docs/index.md, docs/llms.txt, docs/robots.txt
• Repo URLs: github.com/rennf93/ -> github.com/Guard-Core/ across README (hero, badges, ecosystem tables, acknowledgements), mkdocs.yml (repo_name, repo_url, social, feedback), pyproject project.urls, SECURITY.md, issue template, docs pages, AGENTS.md, CLAUDE.md, SKILL.md, llms.txt
• Container references: ghcr.io/rennf93/ -> ghcr.io/guard-core/ in docs/index.md pull examples and the bump_version.py regex so future bumps keep matching
• Shields badge: last-commit owner -> Guard-Core
• GitHub Container Registry org package link -> github.com/orgs/Guard-Core/...
• Emails: pyproject author email -> rennf93@guard-core.com; README author contact and CODE_OF_CONDUCT contact -> contact@guard-core.com
• FUNDING.yml: github: rennf93 -> github: Guard-Core (tidelift and paypal lines kept)
• Bug fix: llms.txt Contributing link pointed at blob/main, repo default branch is master

Intentionally untouched

• CHANGELOG.md and docs/release-notes.md history entries (6 lines)
• mkdocs.yml author profile url (personal profile)
• .github/workflows/docs.yml and .github/workflows/release.yml uses: references to rennf93/github-actions-secrets-mgmt and rennf93/upsert-context7: those action repositories do not exist under Guard-Core yet (404), so repointing them here would break the docs deploy and release pipelines

Verification

• uv run ruff format --check + uv run ruff check on touched Python: clean
• uv run mypy .: 45 pre-existing errors in tests/, byte-identical to the base commit, 0 new; touched bump_version.py clean on its own
• uv run mkdocs build --strict: exit 0, output identical to base, no new errors
• uv run pymarkdownlnt scan: findings identical to base (all inside .venv site-packages), 0 new
• pyproject.toml parses via tomllib on 3.12, urls and author email verified
• git grep -n rennf93 after edits: 11 lines, down from 167
  • 6 history lines (CHANGELOG.md x3, docs/release-notes.md x3), preserved by design
  • 1 mkdocs.yml author personal profile url, per manifest
  • 1 pyproject.toml line is the new author email rennf93@guard-core.com, correct as-is
  • 3 workflow uses: action refs, blocked on the action repos joining the org
• 157 lines changed across 16 files, no comments added, no AI attribution

[github-actions]

Thanks for opening your first pull request on djangoapi-guard!

Quick checklist before review (most of these are enforced by CI, but worth a glance):

• make lint — ruff format, ruff check, mypy, and vulture
• make test (or make local-test) — full test suite passes with 100% coverage
• make security — bandit, safety, and pip-audit all clean
• make quality — radon and xenon complexity thresholds respected
• No # noqa / # type: ignore shortcuts; pre-existing violations in touched files are fixed
• Added an entry under ## Unreleased in CHANGELOG.md
• If you touched a public API, updated the relevant page under docs/
• If the change involves engine logic, the corresponding fix landed in guard-core first

See CONTRIBUTING.md for the full workflow and the Code of Conduct for the community standards we follow.

Welcome aboard — a maintainer will review shortly.