feat: refactor to SI Quiz with Space Invaders arcade interface

- Updated Dockerfile to Python 3.11, selective COPY for cleaner image
- Expanded .gitignore with Python/OS patterns
- Added config.json, questions.json, env_example, and static assets
- Updated templates (host, player, scores) with Space Invaders UI
- Rewrote README for SI Quiz branding and setup docs

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

.gitignore

@@ -1,7 +1,17 @@
+# Runtime data
+data/
+*.db
+
+# Environment
 .env
-*.log
+
+# Python
 __pycache__/
-node_modules/
+*.pyc
+*.pyo
+.venv/
 venv/
-dist/
-build/
+
+# OS
+.DS_Store
+Thumbs.db