docs: Add Docker deployment instructions and build script

- Add build-and-push-docker.ps1 PowerShell script for automated Docker builds
- Update README.md with comprehensive Docker deployment guide
- Include environment variable configuration
- Document automated email scheduling in containers
- Add GitHub Container Registry push instructions

.gitignore

@@ -32,6 +32,9 @@ yarn-error.log*
 # local env files
 .env*.local
 
+# Firebase service account keys
+firebase-service-account.json
+
 # vercel
 .vercel