refactor: migrate LangGraph server from Container App to Azure Web App

## Changes
- Delete Dockerfile and .dockerignore (no longer needed)
- Rewrite deploy-langgraph.yml: zip deploy to Web App (not ACR build)
- Update deploy-langgraph-ui.yml: VITE_LANGGRAPH_URL → soc-langgraph.azurewebsites.net

## Azure Resources
- CREATED: soc-langgraph Web App (Node.js 20, B1 Linux, southeastasia)
- CREATED: soc-langgraph-plan (App Service Plan, B1, southeastasia)
- DELETED: soc-langgraph Container App
- DELETED: soc-cae Container App Environment
- DELETED: socsocacr ACR
- All env vars migrated to Web App
- Startup: npx langgraphjs dev --host 0.0.0.0 --port 2024 --no-browser
- WEBSITES_PORT=2024

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

.github/workflows/deploy-langgraph-ui.yml

@@ -31,7 +31,7 @@ jobs:
       - name: Build Vite frontend
         working-directory: langgraph
         env:
-          VITE_LANGGRAPH_URL: https://soc-langgraph.jollysand-7f0f231b.southeastasia.azurecontainerapps.io
+          VITE_LANGGRAPH_URL: https://soc-langgraph.azurewebsites.net
         run: pnpm vite build
 
       - name: Deploy to Azure Static Web Apps