Add Azure Container Apps deployment with one-command automation

[Copilot]

Implements Azure deployment automation in response to "what is the quickest way to deploy this on Azure?"

Changes

Automation

• azure-deploy.sh - Single-command deployment script (5-10 min)
  • Prerequisites validation (Azure CLI, Docker)
  • Resource provisioning (RG, ACR, Container Apps environment)
  • Cloud-based Docker build via az acr build
  • Automated deployment with retry logic for name collisions

Documentation

• docs/DEPLOY_AZURE.md - Complete guide covering Container Apps (recommended), App Service, Portal UI, and CI/CD setup
• docs/AZURE_QUICK_REFERENCE.md - Copy-paste commands for common operations
• docs/GETTING_STARTED_AZURE.md - Deployment path comparison and cost breakdown

CI/CD

• .github/workflows/azure-deploy.yml - Auto-deployment pipeline with explicit permissions (contents: read, id-token: write)

Core README

• Added prominent Azure deployment section linking to guides

Usage

# Deploys to Azure Container Apps in one command
./azure-deploy.sh

# Manual alternative with full control
az acr build --registry $ACR_NAME --image app:latest .
az containerapp create --name $APP_NAME --image $ACR_NAME.azurecr.io/app:latest ...

Architecture Decision

Chose Azure Container Apps over App Service for:

• Native async/ASGI support (Hypercorn on port 5001)
• Consumption-based pricing (free tier: 180k vCPU-sec/month)
• Automatic HTTPS and scaling
• Modern container-first workflow

Existing Dockerfile already production-ready with multi-stage build (Node 20 → Python 3.11 slim).

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