Remove backend Alpine smoke (PG16) job from CI workflow

The backend Alpine smoke test targeting PostgreSQL 16 was removed from the CI configuration. This cleanup simplifies the workflow by eliminating redundancy, as the functionality might be covered elsewhere or deemed unnecessary.

.github/workflows/pg-compat-matrix.yml

@@ -67,65 +67,3 @@ jobs:
         env:
           PG_DSN_CANDIDATES: postgresql://postgres:postgres@postgres:5432/compatdb?sslmode=disable,postgresql://postgres:postgres@127.0.0.1:5432/compatdb?sslmode=disable
         run: python backend/scripts/pg_compat_smoke.py
-
-  backend-alpine-smoke:
-    name: Backend Alpine smoke (PG16)
-    runs-on: ubuntu-latest
-
-    services:
-      postgres:
-        image: postgres:16
-        env:
-          POSTGRES_DB: compatdb
-          POSTGRES_USER: postgres
-          POSTGRES_PASSWORD: postgres
-        ports:
-          - 5432:5432
-        options: >-
-          --health-cmd "pg_isready -U postgres -d compatdb"
-          --health-interval 5s
-          --health-timeout 5s
-          --health-retries 20
-
-    steps:
-      - name: Checkout
-        uses: actions/checkout@v4
-
-      - name: Enable pg_stat_statements in service container
-        run: |
-          PG_CID="$(docker ps --filter "ancestor=postgres:16" --format "{{.ID}}" | head -n1)"
-          if [ -z "$PG_CID" ]; then
-            echo "Could not find postgres service container for version 16"
-            docker ps -a
-            exit 1
-          fi
-
-          echo "Using postgres container: $PG_CID"
-          docker exec "$PG_CID" psql -U postgres -d compatdb -c "ALTER SYSTEM SET shared_preload_libraries = 'pg_stat_statements';"
-          docker restart "$PG_CID"
-
-          for i in $(seq 1 40); do
-            if docker exec "$PG_CID" pg_isready -U postgres -d compatdb; then
-              break
-            fi
-            sleep 2
-          done
-
-          docker exec "$PG_CID" psql -U postgres -d compatdb -c "CREATE EXTENSION IF NOT EXISTS pg_stat_statements;"
-
-      - name: Build backend image with Alpine base
-        run: |
-          docker build \
-            -f backend/Dockerfile \
-            --build-arg PYTHON_BASE_IMAGE=python:3.13-alpine \
-            -t nexapg-backend-alpine-smoke:ci \
-            ./backend
-
-      - name: Run smoke checks in backend Alpine image
-        env:
-          PG_DSN_CANDIDATES: postgresql://postgres:postgres@127.0.0.1:5432/compatdb?sslmode=disable
-        run: |
-          docker run --rm --network host \
-            -e PG_DSN_CANDIDATES="${PG_DSN_CANDIDATES}" \
-            nexapg-backend-alpine-smoke:ci \
-            python /app/scripts/pg_compat_smoke.py