Expose build commit/branch to templates via SITE_COMMIT/SITE_BRANCH

pelicanconf.py reads them from env vars (blank on a plain local
build); the CI workflow's Build step now sets SITE_COMMIT (short SHA)
and SITE_BRANCH before invoking pelican. Bumps the theme submodule to
pick up the matching footer change (427fd9d).

.gitea/workflows/build-deploy.yml

@@ -59,9 +59,14 @@ jobs:
         # main -> real prod config; staging -> prod-like preview (feeds,
         # absolute URLs) pointed at the dev webserver; devel (or anything
         # else) -> bare pelicanconf.py, same as a plain local build.
+        # SITE_COMMIT/SITE_BRANCH are picked up by pelicanconf.py (and thus
+        # every config that imports it) for the footer build-info line.
         env:
           REF_NAME: ${{ github.ref_name }}
+          GITEA_SHA: ${{ github.sha }}
         run: |
+          export SITE_COMMIT=$(echo "$GITEA_SHA" | cut -c1-8)
+          export SITE_BRANCH="$REF_NAME"
           if [ "$REF_NAME" = "main" ]; then
             pelican -s publishconf.py
           elif [ "$REF_NAME" = "staging" ]; then