A player with nothing to show stops filling its log, and other fixes

Fixes

• A player with an empty playlist, or with an asset it can't show, no longer writes the same log line every few seconds. The viewer logs the first time and stays quiet until something changes. The journal on a player is small, and the repeats pushed out the log lines you'd need after a crash.
• On the Raspberry Pi 2 and 32-bit Pi 3 images, a display that disappears while the player runs no longer leaves the viewer retrying on a black screen first, which at startup could take several minutes. The viewer gives up on the first failed start and its container restarts, which is what finds the display again.
• On the Raspberry Pi 5, x86 and arm64 images, when the viewer restarts itself because it started without seeing a connected display, it logs that as a warning instead of an error, so a recovery that worked no longer sends an error report.

Improvements

• Anthias's usage statistics now include the Anthias version, as version_name, next to the commit and branch they already sent. With analytics_opt_out set in the player's config, nothing is sent, as before.
• The API reference on the Anthias website is built from the API itself and updates when the API changes. The old copy was missing 9 endpoints, including the display power and viewer endpoints.
• The Anthias website has pages on using a Raspberry Pi for digital signage, as an advertising display and as an info screen, a link to the signage app store at signage-apps.com, and a Trust Center link with an FAQ entry on where to get the SBOM. It also says plainly that the Raspberry Pi Imager images are the balenaHub Fleets for Good images, which update over the air.

For contributors

• bun run test runs front-end tests that need a page, using happy-dom, starting with the app settings form.
• New tests for the CEC code, the display schedule, telemetry, image processing and the viewer's log changes.
• The README no longer carries the broken Star History chart or the stale "Issues and Bugs" note.

Django REST framework, uvicorn, Python development tools and the GitHub Actions used in CI, including CodeQL, were updated.