feat: create production Dockerfile (#37)

- Multi-stage build for optimal image size
- Alpine Linux base (~220MB total)
- Non-root user for security (nodejs:1001)
- dumb-init for proper signal handling
- Built-in health check endpoint
- Production dependencies only
- Comprehensive .dockerignore
- Health check API endpoint
- Docker deployment documentation

Features:
- Optimized layer caching
- Secure non-root execution
- Container health monitoring
- ~220MB final image size
- Ready for Kubernetes/Docker Compose

Closes #37

.dockerignore

@@ -0,0 +1,68 @@
+# Dependencies
+node_modules
+app/node_modules
+supabase/node_modules
+
+# Build outputs
+.nuxt
+app/.nuxt
+.output
+app/.output
+dist
+app/dist
+
+# Logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+pnpm-debug.log*
+lerna-debug.log*
+
+# Environment files (use docker env vars instead)
+.env
+.env.local
+.env.*.local
+app/.env
+app/.env.local
+
+# Editor directories and files
+.vscode/
+.idea/
+*.suo
+*.ntvs*
+*.njsproj
+*.sln
+*.sw?
+.DS_Store
+
+# Git
+.git
+.gitignore
+.gitattributes
+
+# CI/CD
+.github
+.gitea
+
+# Documentation
+*.md
+docs/
+!README.md
+
+# Tests
+test/
+tests/
+*.spec.js
+*.spec.ts
+*.test.js
+*.test.ts
+
+# Temporary files
+*.tmp
+*.bak
+*.swp
+.cache
+
+# Supabase (handled separately)
+supabase/