Enforce no JFrog proxy URLs in committed lockfiles

Run make fix-lockfile in the fmt job and fail on git diff, catching
any accidentally committed JFrog proxy URLs in lockfile.json. Same
CI enforcement pattern as the Python SDK.

Author: mihaimitrea-db

.github/workflows/push.yml

@@ -35,6 +35,11 @@ jobs:
       - name: Check formatting
         run: mvn --errors spotless:check
 
+      - name: Check for JFrog proxy URLs in lockfiles
+        run: |
+          make fix-lockfile
+          git diff --exit-code -- '**/lockfile.json'
+
   unit-tests:
     strategy:
       fail-fast: false