fix: use Oryx server-side build instead of pre-bundled packages

The previous workflow installed dependencies with pip --target and zipped
them into the deployment package. Azure Oryx runtime could not find
the packages because it looks for antenv/ or __oryx_packages__/, not
.python_packages/. Switch to deploying source-only zip with az webapp
deploy, letting SCM_DO_BUILD_DURING_DEPLOYMENT=true trigger Oryx to
run pip install on the server and create the antenv virtualenv.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/deploy-backend.yml

@@ -20,16 +20,10 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@v4
 
-      - name: Set up Python 3.12
-        uses: actions/setup-python@v5
-        with:
-          python-version: "3.12"
-
       - name: Create deployment package
         run: |
           cd backend
-          pip install -r requirements.txt --target=".python_packages/lib/site-packages"
-          zip -r ../deploy.zip . -x ".venv/*" ".env" "__pycache__/*" "*.pyc"
+          zip -r ../deploy.zip . -x ".venv/*" ".env" "__pycache__/*" "*.pyc" ".git/*" "tests/*"
 
       - name: Login to Azure
         uses: azure/login@v2
@@ -38,8 +32,11 @@ jobs:
           tenant-id: ${{ secrets.AZUREAPPSERVICE_TENANTID_62D66D4E65AC4A6C872064AD668AC691 }}
           subscription-id: ${{ secrets.AZUREAPPSERVICE_SUBSCRIPTIONID_5D7B0564A55F4209A91149F2642D3F69 }}
 
-      - name: Deploy to Azure Web App
-        uses: azure/webapps-deploy@v3
-        with:
-          app-name: soc-backend
-          package: deploy.zip
+      - name: Deploy to Azure Web App (Oryx build)
+        run: |
+          az webapp deploy \
+            --name soc-backend \
+            --resource-group Operation \
+            --src-path deploy.zip \
+            --type zip \
+            --async false