Add Docker support and fix rating change extraction

- Add Dockerfile with optimized Puppeteer configuration for containers
- Add .dockerignore for efficient builds
- Fix rating change regex to match actual PDGA format (no brackets)
- Update Puppeteer launch args for Docker compatibility
- Use new headless mode to resolve deprecation warning

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

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

.dockerignore

@@ -0,0 +1,7 @@
+node_modules
+.git
+.gitignore
+README.md
+Dockerfile
+.dockerignore
+*.log