ci: auto-version every push as dev-DATE with nightly-DATE image tag

Push builds now bake VERSION=dev-YYYYMMDD and additionally tag the
image nightly-YYYYMMDD, so a dated, identifiable artifact exists without
creating a git tag. Explicit v* tags keep tagging IMAGE:vX.Y.Z.

.gitea/workflows/build.yaml

@@ -29,9 +29,15 @@ jobs:
           SHA=$(git rev-parse --short HEAD)
           FULL_SHA=$(git rev-parse HEAD)
           IMAGE="git.kubebase.de/${{ gitea.repository }}"
-          if [ "${{ gitea.ref_type }}" = "tag" ]; then VERSION="${{ gitea.ref_name }}"; else VERSION=""; fi
-          TAGS="-t ${IMAGE}:sha-${SHA} -t ${IMAGE}:latest"
-          if [ -n "$VERSION" ]; then TAGS="${TAGS} -t ${IMAGE}:${VERSION}"; fi
+          DATE_STAMP=$(date -u +"%Y%m%d")
+          if [ "${{ gitea.ref_type }}" = "tag" ]; then
+            VERSION="${{ gitea.ref_name }}"
+            VERSION_TAG="${{ gitea.ref_name }}"
+          else
+            VERSION="dev-${DATE_STAMP}"
+            VERSION_TAG="nightly-${DATE_STAMP}"
+          fi
+          TAGS="-t ${IMAGE}:sha-${SHA} -t ${IMAGE}:latest -t ${IMAGE}:${VERSION_TAG}"
           docker build --no-cache \
             --build-arg COMMIT_SHA="$FULL_SHA" \
             --build-arg BUILD_DATE="$(date -u +"%Y-%m-%dT%H:%M:%SZ")" \
@@ -39,7 +45,7 @@ jobs:
             $TAGS .
           docker push "${IMAGE}:sha-${SHA}"
           docker push "${IMAGE}:latest"
-          if [ -n "$VERSION" ]; then docker push "${IMAGE}:${VERSION}"; fi
+          docker push "${IMAGE}:${VERSION_TAG}"
 
       - name: Update k8s manifest in admin/apps
         env: