feat: implement automated Docker deployment and update README

- Replaced manual rsync/npm_deploy workflow with multi-stage Docker builds.
- Added Dockerfile and .dockerignore for staging and production environments.
- Added 'deploy:staging' and 'deploy:prod' scripts to package.json.
- Updated README.md with new deployment instructions.

.dockerignore

@@ -0,0 +1,12 @@
+node_modules
+build
+.svelte-kit
+.git
+.env
+.env.*
+!.env.staging
+!.env.prod
+npm_deploy
+test-results
+test_results
+documentation