[Feature]: Connection link on Settings page wraps to 3 lines — needs copy button instead

### Problem Statement

On the Settings page (`/settings`), the trackpad connection URL (with auth token) is shown as raw wrapped text below the QR code. Since the full URL is long, it wraps across 3 lines, which makes the UI look cluttered and less polished. There's no easy way to copy the link — users have to manually select the wrapped text.

### Proposed Solution

Replace the raw multi-line URL text with a compact, single-line component:

- Show a truncated preview of the URL (e.g. `172.16.44.65:3000/trackpad...`) in a single line
- Add a copy icon button next to it that copies the full URL (including the auth token) to the clipboard
- Show brief visual feedback on click — icon/label changes to a checkmark and "Copied" for ~1.5 seconds, then reverts

This keeps the Settings page clean and gives users a fast, one-click way to share the connection link instead of manually selecting wrapped text.

### Alternatives Considered (Optional)

- Keeping the full URL as plain text but reducing font size / breaking it differently — doesn't fully solve the clutter issue and is still hard to copy accurately.
- Showing only the QR code and removing the text link entirely — but some users may not have a camera-based scan option handy, so a copyable link is still useful as a fallback.

### Additional Context (Optional)

Happy to work on this and submit a PR with the implementation. Can share a quick UI mockup of the proposed copy-button design if helpful for review before starting work.

### Checklist

- [x] I have searched for existing feature requests to avoid duplicates