feat: repository file freshness system (script + config)

[buddingengineers12345]

Builds the repository file freshness system.

What’s included

• scripts/repo_file_freshness.py: generates freshness data using Git only (git ls-files + last commit per file).
• freshness_ignore.json: configurable ignore rules (files/dirs/extensions/globs) → Blue.
• Generated artifacts:
  • docs/repo_file_status_report.md (dashboard)
  • file_freshness.json (per-file details)
  • freshness_summary.json (counts + badge fields)
• just freshness to run locally.
• tests/test_repo_file_freshness.py: ephemeral git repos covering classification + ignore + edge cases.
• .github/workflows/file-freshness.yml: scheduled + manual workflow that regenerates artifacts and commits/pushes only when changed (no on: push to avoid loops).

CI stability fix (included)

• Updates tests/test_template.py to use git+file://... template sources instead of . for Copier invocations, avoiding git hardlink clone failures in containerized filesystems.

Notes

• Repo-wide docs/ is ignored by default in .gitignore; this PR adds an exception for docs/repo_file_status_report.md so the dashboard can be tracked.