The MIT-branch copyright line in LICENSE.jinja was hardcoded to a stale
`2011-2022` range. Rather than introduce a render-time dependency
(`jinja2_time`) that every template consumer would need installed
alongside copier, keep the rendered LICENSE as plain text and let this
repo's own Renovate bump the literal year once a year. Consumers pick up
the new year on their next `copier update`, with no added dependencies.

- LICENSE.jinja: bump baseline to `2011-2026` (plain literal, no markers)
- renovate.json: add a `custom.current-year` customDatasource that reads
  the current year from timeapi.io, a dedicated regex manager that
  targets only the 4-digit year on the LICENSE line, and an automerge
  packageRule so the once-a-year bump merges itself.

The external time API is only ever contacted during this repo's Renovate
runs, never by consumers.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

feat: keep LICENSE copyright year current via Renovate

See merge request !766