switch to a dedicated cache repo

.forgejo/workflows/ci.yml

@@ -15,6 +15,7 @@ jobs:
       POSTGRES_IMG_DIGEST: ${{ secrets.POSTGRES_IMG_DIGEST }}
       RUST_IMG_DIGEST: ${{ secrets.RUST_IMG_DIGEST }}
       PREBUILT_BACKEND_TEST_IMAGE: ${{ secrets.REGISTRY_HOST }}/${{ github.repository }}/sharenet-test-rust
+      CACHE_REPO: ${{ secrets.REGISTRY_HOST }}/${{ github.repository }}/sharenet-test-rust-cache
 
     steps:
       - name: Checkout code
@@ -59,6 +60,9 @@ jobs:
         run: |
           # Build deps stage with layer caching
           podman --remote build \
+            --layers \
+            --cache-to   "$CACHE_REPO" \
+            --cache-from "$CACHE_REPO" \
             --target deps \
             -f backend/Dockerfile.test-rust \
             -t "$PREBUILT_BACKEND_TEST_IMAGE:deps-${{ steps.cache-key.outputs.cache_key }}" \
@@ -70,11 +74,12 @@ jobs:
         run: |
           # Build final image using cached deps
           podman --remote build \
+            --layers \
+            --cache-from "$CACHE_REPO" \
             --target runner \
             -f backend/Dockerfile.test-rust \
             -t "$PREBUILT_BACKEND_TEST_IMAGE:test-${{ github.sha }}" \
-            --cache-from "$PREBUILT_BACKEND_TEST_IMAGE:deps-${{ steps.cache-key.outputs.cache_key }}" \
-            --layers
+            .
 
       - name: Start PostgreSQL
         run: |