ci: add one-time version check workflow

.github/workflows/test-version.yml

@@ -0,0 +1,22 @@
+name: One time version test
+
+on: [push, pull_request]
+
+jobs:
+  deploy:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: 3.12
+      - name: Setup Poetry
+        uses: Gr1N/setup-poetry@v9
+      - name: Install deps
+        run: poetry install
+      - name: Assert tag version matches __version__ attribute
+        run: |
+          python -c "import sys; sys.path.pop(0); \
+            import aleph_alpha_client; \
+            assert aleph_alpha_client.__version__ == '7.5.0'"