Use Docker Metadata Action for automatic lowercase conversion

Replace manual tag generation with docker/metadata-action which:
- Automatically converts repository names to lowercase for GHCR
- Generates proper OCI-compliant labels
- Provides better tag management

This fixes the "repository name must be lowercase" error.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: jcrapuchettes

.github/workflows/ci.yaml

@@ -39,19 +39,27 @@ jobs:
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
+      - name: Extract metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ghcr.io/${{ github.repository }}
+          tags: |
+            type=raw,value=${{ matrix.pg_version.major }}
+            type=raw,value=${{ matrix.pg_version.full }}
+            type=raw,value=${{ steps.tag.outputs.TAG }}-${{ matrix.pg_version.major }}
+
       - name: Build and push release
         uses: docker/build-push-action@v6
         with:
           context: .
           file: ./pg${{ matrix.pg_version.major }}/Dockerfile
           push: true
-          tags: |
-            ghcr.io/${{ github.repository }}:${{ matrix.pg_version.major }}
-            ghcr.io/${{ github.repository }}:${{ matrix.pg_version.full }}
-            ghcr.io/${{ github.repository }}:${{ steps.tag.outputs.TAG }}-${{ matrix.pg_version.major }}
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
           build-args: |
             PG_VERSION=${{ matrix.pg_version.full }}
-            PG_MAJOR_VERSION=${{ matrix.pg_version.full }}
+            PG_MAJOR_VERSION=${{ matrix.pg_version.major }}
             VERSION=${{ steps.tag.outputs.TAG }}
           cache-from: type=gha
           cache-to: type=gha,mode=max

.github/workflows/push.yml

@@ -105,13 +105,22 @@ jobs:
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
 
+      - name: Extract metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ghcr.io/${{ github.repository }}
+          tags: |
+            type=raw,value=${{ matrix.pg_version.major }}-latest
+
       - name: Build and push latest
         uses: docker/build-push-action@v6
         with:
           context: .
           file: ./pg${{ matrix.pg_version.major }}/Dockerfile
           push: true
-          tags: ghcr.io/${{ github.repository }}:${{ matrix.pg_version.major }}-latest
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
           build-args: |
             PG_VERSION=${{ matrix.pg_version.full }}
             PG_MAJOR_VERSION=${{ matrix.pg_version.major }}