ScoreSight

A phone as the camera, a smoother preview, and clock fixes from the
Discussions: soccer clocks past 59 minutes, and clocks whose colon isn't
read while they're stopped.

### Added

- **Phone camera.** A new source: an iPhone or Android phone sends its camera to ScoreSight over Wi-Fi, from its browser, with no app to install. Choose **Phone camera** in the Source list and scan the QR code the picture shows. ScoreSight serves the phone's page over HTTPS (phone browsers open the camera only on a secure page) on the port after the HTTP server's, with a certificate of its own, so the phone warns once that the connection isn't private. The phone sends a picture per detection; while none comes, the boxes aren't read ([Video Sources: Phone camera](https://royshil.github.io/scoresight/sources.html#phone-camera)).
- **Smooth preview.** **View > Smooth preview** refreshes the picture in the viewer up to 20 times a second (15 for a 30 fps source) instead of about once, so a running clock moves like video. It uses more CPU; the readings and the outputs don't change. Off by default ([#165](https://github.com/royshil/scoresight/discussions/165)).

### Fixed

- **A clock read without it