Clean up unused files and tracked junk

Remove the duplicate fancy-wordle-modern.html page, the standalone intro
prototype, the CSS backup and an unused image. Stop tracking .DS_Store and
Playwright MCP logs, and refresh IMPROVEMENTS.md.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Dockerfile

@@ -2,7 +2,6 @@ FROM nginx:alpine
 
 COPY index.html /usr/share/nginx/html/index.html
 COPY CSS /usr/share/nginx/html/CSS
-COPY img /usr/share/nginx/html/img
 COPY Celebration.mp3 dictionary.json script.js supabase-config.js targetWords.json word-data.js /usr/share/nginx/html/
 
 EXPOSE 80