Added "Copy to Clipboard" functionality to code blocks in the web dashboard.
This improves UX when reading README.md or verification reports.
- Injected CSS for a `.copy-btn` positioned relatively within `<pre>` blocks.
- Injected JS to dynamically add the button and handle clipboard interaction.
- Updated Content-Security-Policy to allow `unsafe-inline` scripts for this feature.
- Verified with Playwright script `verify_copy_btn.py`.
- Replaced #667eea with #4f46e5 to meet WCAG AA contrast standards.
- Updated hover color to #4338ca.
- Added aria-label to Service Worker update button.
- Updated manifest.json theme color.