ci(contracts): install api/requirements.txt before generating OpenAPI

Author: Faxbot Agent

.github/workflows/build.yml

@@ -46,6 +46,10 @@ jobs:
         uses: actions/setup-python@v5
         with:
           python-version: '3.11'
+      - name: Install Python deps for OpenAPI generation
+        run: |
+          python -m pip install --upgrade pip
+          pip install -r api/requirements.txt
       - name: Install jsonschema
         run: |
           python -m pip install --upgrade pip
@@ -122,4 +126,3 @@ jobs:
         working-directory: api/admin_ui
         run: npm run build
 
-