Add better documentation and scripts for air-gapped deployment

Created new helper scripts:
- quickstart-airgap.sh: One-command deployment for restricted environments
- check-ready.sh: Validates that pre-built files exist before deployment

Updated documentation:
- Enhanced Dockerfile.frontend.prebuilt with clearer error messages
- Updated DEPLOYMENT.md with step-by-step quick start guide
- Updated README.md to distinguish standard vs air-gapped deployment

Key improvements:
- Clear warning that build must happen BEFORE docker-compose
- Helper script that combines build + deployment steps
- Readiness check to catch missing pre-built files early
- Better instructions for test environments with restricted npm access

This addresses the common error where Docker fails because
frontend/dist/frontend/browser doesn't exist yet.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Dockerfile.frontend.prebuilt

@@ -1,10 +1,15 @@
 # Dockerfile for pre-built Angular frontend (air-gapped/restricted environments)
-# Build the Angular app locally first: cd frontend && npm run build:prod
-# Then use this Dockerfile to package the pre-built files
+#
+# IMPORTANT: You must build the Angular app BEFORE running docker-compose!
+# Run this command first: ./build-for-airgap.sh
+# OR manually: cd frontend && npm install && npm run build:prod
+#
+# This Dockerfile expects frontend/dist/frontend/browser to exist
 
 FROM nginx:alpine
 
 # Copy pre-built Angular app to nginx
+# If this step fails, you need to run: ./build-for-airgap.sh
 COPY frontend/dist/frontend/browser /usr/share/nginx/html
 
 # Copy nginx configuration