fix(ci): lowercase GHCR image ref for the multi-arch publish workflow

The v1.4.25 W11a refactor moved the workflow off `docker/metadata-action`
as the single source of the image-ref string and started passing
`${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}` directly into the
`outputs:` of `docker/build-push-action`. `IMAGE_NAME` comes from
`github.repository` (`MBombeck/HealthLog`), and GHCR rejects pushes
with any uppercase character in the repo segment, so both per-platform
builds failed with `invalid reference format`. Resolve the lowercase
form once at the top of each job via `${VAR,,}` bash expansion and
reuse it across `metadata-action`, `build-push-action`, and the
`buildx imagetools` calls in the merge stage.

.github/workflows/docker-publish.yml

@@ -65,6 +65,18 @@ jobs:
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
 
+      # GHCR rejects repository refs with uppercase letters. `IMAGE_NAME`
+      # is derived from `github.repository`, which preserves the case of
+      # the GitHub org/user (`MBombeck/HealthLog`). `docker/metadata-action`
+      # lowercases its `images:` input transparently, so the legacy
+      # single-job workflow worked; the multi-arch matrix now feeds
+      # `outputs:` of build-push-action directly and needs the lowercase
+      # form there too. Resolve it once at the top of the job and reuse
+      # via $GITHUB_ENV.
+      - name: Lowercase image ref
+        run: |
+          echo "IMAGE_REF=${REGISTRY}/${IMAGE_NAME,,}" >> "$GITHUB_ENV"
+
       # Skip login on PRs from forks — they don't have package:write.
       # Image is built but not pushed in that case.
       - name: Log in to GitHub Container Registry
@@ -79,7 +91,7 @@ jobs:
         id: meta
         uses: docker/metadata-action@v5
         with:
-          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          images: ${{ env.IMAGE_REF }}
           labels: |
             org.opencontainers.image.title=HealthLog
             org.opencontainers.image.description=Self-hosted health-tracking PWA
@@ -100,7 +112,7 @@ jobs:
           platforms: ${{ matrix.platform }}
           labels: ${{ steps.meta.outputs.labels }}
           outputs: |
-            type=image,name=${{ env.REGISTRY }}/${{ env.IMAGE_NAME }},push-by-digest=true,name-canonical=true,push=${{ github.event_name != 'pull_request' }}
+            type=image,name=${{ env.IMAGE_REF }},push-by-digest=true,name-canonical=true,push=${{ github.event_name != 'pull_request' }}
           cache-from: |
             type=gha,scope=build-${{ matrix.cache_scope }}-${{ github.ref_name }}
             type=gha,scope=build-${{ matrix.cache_scope }}-main
@@ -156,6 +168,12 @@ jobs:
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
 
+      # GHCR requires the repository ref to be lowercase. See the same
+      # step in the `build` job above for the longer rationale.
+      - name: Lowercase image ref
+        run: |
+          echo "IMAGE_REF=${REGISTRY}/${IMAGE_NAME,,}" >> "$GITHUB_ENV"
+
       - name: Log in to GitHub Container Registry
         uses: docker/login-action@v3
         with:
@@ -167,7 +185,7 @@ jobs:
         id: meta
         uses: docker/metadata-action@v5
         with:
-          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          images: ${{ env.IMAGE_REF }}
           tags: |
             type=ref,event=branch
             type=ref,event=pr
@@ -186,11 +204,11 @@ jobs:
         run: |
           # shellcheck disable=SC2046,SC2086
           docker buildx imagetools create $(jq -cr '.tags | map("-t " + .) | join(" ")' <<< "$DOCKER_METADATA_OUTPUT_JSON") \
-            $(printf '${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}@sha256:%s ' *)
+            $(printf '${{ env.IMAGE_REF }}@sha256:%s ' *)
 
       - name: Inspect published manifest
         run: |
-          docker buildx imagetools inspect '${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}:${{ steps.meta.outputs.version }}'
+          docker buildx imagetools inspect '${{ env.IMAGE_REF }}:${{ steps.meta.outputs.version }}'
 
       # Phase C2 (v1.4.15): trigger Coolify deploy automatically once GHCR has
       # the new image. Removes the manual SSH + force-pull recipe documented