build.yml: annotate the rolling 'latest' tag, so its release stays on top

Forgejo orders the releases page by each release's creation time and
resets that time from the tag at every tag push: a lightweight tag gives
the tagged commit's time, an annotated tag the tagger's. A push's dated
release is tagged at push time, after its commits, so the lightweight
'latest' tag always sorted below it (2026-11-01: 'latest' created
01:09:36Z = the tip's commit time, the dated release 02:02:09Z = its
tag's time). An annotated tag made when the run ends is newer than any
dated release tagged before the images were built.

.forgejo/workflows/build.yml

@@ -108,7 +108,11 @@ jobs:
           git config --global --add safe.directory "$PWD"
           git config user.email "ci@catcrafts.net"
           git config user.name "fp6-img CI"
-          git tag -f latest
+          # Annotated, so the release keeps the top of the releases page:
+          # Forgejo stamps a release with its tag's time at every tag push -
+          # a lightweight tag's is the commit's, older than the dated release
+          # tagged at push time; an annotated tag's is now.
+          git tag -a -f latest -m "Latest FP6 Nura image, built $(date -u +%Y-%m-%d) from $(git rev-parse --short HEAD)"
           git push origin latest --force
 
       - name: Publish rolling 'latest' release