Improve copyright year range handling

[scal444]

Implements #161

[scal444]

@greptile-apps please review the changes to apply_copyright.sh, they're the only non-automated bit

[greptile-apps]

Confidence Score: 5/5

The PR appears safe to merge, with the previous copyright-fixer issue fully addressed and no new actionable failures identified.

Summary

• Accepts and replaces both single years and year ranges.
• Clamps imported pre-project history to the 2025 project baseline.
• Includes the current year for pending working-tree changes so local fixes agree with subsequent CI checks.
• The previously reported stale-year fixer issue is resolved.

_{Reviews (2) · Last reviewed commit: "Improve copyright year range handling"}

[scal444]

@greptile-apps please re-review copyright application

[evasnow1992]

Changes look good to me.

[greptile-apps]

Too many files changed for review (170 files, 100 file limit).

Bypass the limit by tagging @greptile-apps to review.