version-bump-check: support date-based version tags

[mairas]

Problem

The version-bump-check.yml tag regex only matches semver-style tags (v0.3.5+1):

^v[0-9]+\.[0-9]+\.[0-9]+(\.[0-9]+)?\+[0-9]+$

halos-pi-gen uses date-based tags (v2026-03-17.0-1), which don't match. This causes the check to silently skip with "No stable release tags found."

Additionally, config.* files are excluded from package-affecting changes (line 101), which is correct for Docker/app configs but not for pi-gen image configs.

Current workaround

halos-pi-gen has a local image-version-check job in its PR workflow that handles date-based versions (PR halos-org/halos-pi-gen#86).

Possible fix

Either:

1. Broaden the tag regex to also match date-based versions
2. Allow repos to pass custom tag patterns and package-affecting file patterns as workflow inputs