Add real Nostr integration test

.github/workflows/python-ci.yml

@@ -63,6 +63,9 @@ jobs:
         run: |
           python -m pip install --upgrade pip
           pip install -r src/requirements.txt
+      - name: Enable Nostr network tests on main branch
+        if: github.ref == 'refs/heads/main'
+        run: echo "NOSTR_E2E=1" >> $GITHUB_ENV
       - name: Run tests with coverage
         shell: bash
         run: |