ci: free disk on GH runner, prune Docker cache, and reliable self-hosted fallback

- Add “Free Disk Space (Ubuntu)” and Docker prune steps before/after the GitHub-hosted build to recover tens of GB and avoid “no space left on device” failures on ubuntu-latest.
- Remove continue-on-error and gate the self-hosted job with `always() && needs.build-gh.result != 'success'` so it runs only if the GH build fails, while publish proceeds if either path succeeds.
- Enable buildx GHA cache (cache-from/cache-to) to minimize runner disk pressure and rebuild times without loading images locally.

.github/workflows/build-release.yml

@@ -20,6 +20,7 @@ jobs:
         with:
           fetch-depth: 0
           fetch-tags: true
+
       - name: Install prerequisites (jq, curl)
         run: |
           set -e
@@ -27,6 +28,7 @@ jobs:
             sudo apt-get update -y
             sudo apt-get install -y jq curl
           fi
+
       - name: Determine current tag (release, then git fallback)
         id: resolve
         shell: bash
@@ -47,14 +49,34 @@ jobs:
     name: Build on GitHub Runner (primary)
     needs: check-tag
     runs-on: ubuntu-latest
-    outputs:
-      build_succeeded: ${{ steps.set_out.outputs.succeeded }}
     steps:
       - uses: actions/checkout@v4
         with:
           fetch-depth: 0
           fetch-tags: true
 
+      - name: Show disk usage (pre)
+        run: df -h | sed 's/\s\+/ /g'
+
+      - name: Free Disk Space (Ubuntu)
+        uses: jlumbroso/free-disk-space@main
+        with:
+          tool-cache: false
+          android: true
+          dotnet: true
+          haskell: true
+          large-packages: true
+          docker-images: true
+          swap-storage: true
+
+      - name: Prune Docker caches (pre)
+        run: |
+          docker builder prune -af || true
+          docker system prune -af --volumes || true
+
+      - name: Show disk usage (post-clean)
+        run: df -h | sed 's/\s\+/ /g'
+
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
         with:
@@ -89,7 +111,6 @@ jobs:
       - name: Build and Push (GH runner)
         id: build
         uses: docker/build-push-action@v6
-        continue-on-error: true
         with:
           context: .
           file: ./Dockerfile
@@ -97,19 +118,22 @@ jobs:
           push: true
           provenance: false
           sbom: false
+          cache-from: type=gha,scope=gh
+          cache-to: type=gha,mode=max,scope=gh
           tags: |
             ${{ env.IMAGE_NAME }}:${{ needs.check-tag.outputs.current_tag }}
             ${{ env.IMAGE_NAME }}:latest
 
-      - name: Set outcome flag
-        id: set_out
+      - name: Prune Docker caches (post)
+        if: always()
         run: |
-          echo "succeeded=${{ steps.build.outcome == 'success' }}" >> "$GITHUB_OUTPUT"
+          docker builder prune -af || true
+          docker system prune -af --volumes || true
 
   build-self:
     name: Build on Self-Hosted (fallback)
     needs: [check-tag, build-gh]
-    if: needs.build-gh.outputs.build_succeeded != 'true'
+    if: ${{ always() && needs.build-gh.result != 'success' }}
     runs-on: [self-hosted, linux, x64, homelab]
     steps:
       - uses: actions/checkout@v4
@@ -157,14 +181,22 @@ jobs:
           push: true
           provenance: false
           sbom: false
+          cache-from: type=gha,scope=gh
+          cache-to: type=gha,mode=max,scope=gh
           tags: |
             ${{ env.IMAGE_NAME }}:${{ needs.check-tag.outputs.current_tag }}
             ${{ env.IMAGE_NAME }}:latest
 
+      - name: Prune Docker caches (post)
+        if: always()
+        run: |
+          docker builder prune -af || true
+          docker system prune -af --volumes || true
+
   publish:
     name: Update Release
     needs: [check-tag, build-gh, build-self]
-    if: always() && (needs.build-gh.outputs.build_succeeded == 'true' || needs.build-self.result == 'success')
+    if: ${{ always() && (needs.build-gh.result == 'success' || needs.build-self.result == 'success') }}
     runs-on: ubuntu-latest
     steps:
       - name: Update GitHub Release (same tag)
@@ -188,7 +220,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Fail if both build paths failed
-        if: ${{ !(needs.build-gh.outputs.build_succeeded == 'true' || needs.build-self.result == 'success') }}
+        if: ${{ !(needs.build-gh.result == 'success' || needs.build-self.result == 'success') }}
         run: |
           echo "Manual rebuild failed on both GitHub-hosted and self-hosted paths."
           exit 1