Add .dockerignore for optimized Docker builds

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.dockerignore

@@ -1,27 +1,21 @@
-# Git
+node_modules
 .git
 .gitignore
-
-# Development
-node_modules
-.next
-.cache
-
-# Documentation
-README.md
-CLAUDE.md
 *.md
-
-# IDE
-.idea
+.env*
+Dockerfile
+docker-compose*.yml
+.dockerignore
+backlog
+.next
+out
+.cache
+dist
+build
+coverage
+.github
 .vscode
-*.swp
-
-# OS
-.DS_Store
-Thumbs.db
-
-# Environment (keep .env.example)
-.env
-.env.local
-.env*.local
+.idea
+__pycache__
+*.pyc
+.pytest_cache