fix: Dockerfile build mem-cli binary + CI builds and pushes on all events

- rust:1.81 → rust:1-bookworm (track latest stable)
- cargo build --release → cargo build --release -p mem-cli
- Build + push runs on PRs too (verify image works before merge)

.gitea/workflows/build.yaml

@@ -43,7 +43,6 @@ jobs:
             -f Dockerfile .
 
       - name: Registry login
-        if: github.event_name == 'push' || github.event_name == 'workflow_dispatch'
         run: |
           echo "${REGISTRY_TOKEN}" | docker login "${REGISTRY}" \
             --username "${REGISTRY_USER}" --password-stdin
@@ -52,12 +51,10 @@ jobs:
           REGISTRY_TOKEN: ${{ secrets.FORGEJO_REGISTRY_TOKEN }}
 
       - name: Push Docker image
-        if: github.event_name == 'push' || github.event_name == 'workflow_dispatch'
         run: |
           docker push "${IMAGE}:${{ steps.sha.outputs.short_sha }}"
           docker push "${IMAGE}:latest"
           echo "✓ Pushed: ${IMAGE}:${{ steps.sha.outputs.short_sha }}"
 
       - name: Prune unused images
-        if: github.event_name == 'push' || github.event_name == 'workflow_dispatch'
         run: docker image prune -a --force 2>&1 | tail -3 || true