chore: make contributor tooling work; fix drifted docs (#648)

- mypy.ini parses again (multi-line exclude and inline value comments made
  mypy reject the file); the mypy pre-commit hook is manual-only until the
  ~500 existing errors in src/ are paid down, and CONTRIBUTING says so
- .gitignore: ignore all of config/ except the templates (ytm_auth.json and
  others weren't ignored)
- .gitattributes: LF for .sh and .service
- claude-code-review: skip fork PRs, which have no secrets
- check_system_compatibility.sh: 3.13 supported, <3.10 an error
- docs/scripts drift: emulator guide, README API Metrics, route count,
  docs index, scripts README; pyflakes nits in dev scripts

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -948,7 +948,7 @@ sudo systemctl enable ledmatrix-web.service
 - **On-Demand Controls**: Start specific displays (weather, stocks, sports) on demand
 - **Service Management**: Start/stop the main display service
 - **System Controls**: Restart, update code, and manage the system
-- **API Metrics**: Monitor API usage and system performance
+- **System Stats**: CPU, memory and temperature on the Overview tab
 - **Logs**: View system logs in real-time
 
 ### Troubleshooting Web Interface