docs(release): link container package from release pages

[tulayha]

Summary

• Add a direct link to the VidXP GHCR package page in rendered release and prerelease introductions.
• Derive the package-page URL from the repository passed to the release-note renderer.
• Verify that both stable and beta release notes contain the package link.

This changes release documentation only. It does not change container publication or runtime behavior.

Validation

• PYTHONPATH=. uv run --no-sync pytest -q -p no:cacheprovider tests/test_release_notes.py — 3 passed
• uv run --no-sync ruff check utils/render_release_notes.py tests/test_release_notes.py
• npx --yes markdownlint-cli2@0.23.2
• lychee "**/*.md" ".github/**/*.md" ".agents/**/*.md" — 707 links found, 0 errors
• git diff --check

BEGIN_COMMIT_OVERRIDE
chore(docs): link the container package from release pages
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