chore: remove manual deploy workflow, use Azure native CD

Azure Container App auto-deploy workflow replaces our manual
deploy-langgraph.yml. CD is now managed via Azure Portal.

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

.github/workflows/deploy-langgraph.yml

@@ -1,45 +0,0 @@
-name: Deploy LangGraph Server to Azure Container App
-
-on:
-  push:
-    branches: [main]
-    paths:
-      - "langgraph/**"
-      - ".github/workflows/deploy-langgraph.yml"
-  workflow_dispatch:
-
-permissions:
-  id-token: write
-  contents: read
-
-jobs:
-  build-and-deploy:
-    runs-on: ubuntu-latest
-
-    steps:
-      - name: Checkout code
-        uses: actions/checkout@v4
-
-      - name: Login to Azure
-        uses: azure/login@v2
-        with:
-          client-id: ${{ secrets.AZUREAPPSERVICE_CLIENTID_E361D63054AD449285A5D65AA4425533 }}
-          tenant-id: ${{ secrets.AZUREAPPSERVICE_TENANTID_62D66D4E65AC4A6C872064AD668AC691 }}
-          subscription-id: ${{ secrets.AZUREAPPSERVICE_SUBSCRIPTIONID_5D7B0564A55F4209A91149F2642D3F69 }}
-
-      - name: Build and push to ACR
-        run: |
-          az acr build \
-            --registry socsocacr \
-            --resource-group AuthData \
-            --image soc-langgraph:${{ github.sha }} \
-            --image soc-langgraph:latest \
-            --file langgraph/Dockerfile \
-            langgraph/
-
-      - name: Deploy to Container App
-        run: |
-          az containerapp update \
-            --name soc-langgraph \
-            --resource-group Operation \
-            --image socsocacr.azurecr.io/soc-langgraph:${{ github.sha }}