v0.59.0

The freshness dot on a card and the two error messages stay legible on a dark theme. They were drawn in fixed colours straight onto the theme's own surface, where they reached 2.6:1 against a 3:1 requirement. They now take a third of the theme's text colour, which darkens them on a light theme and lightens them on a dark one. The badges are unchanged: they bring their own background and were never the problem.

The German translations are now checked by the test suite: both shipped catalogues have to be complete, cover the same strings, and de_CH has to be de_DE with the sharp s resolved to ss. An untranslated string is invisible to everyone except the person reading the wrong language, which is how a whole settings tab shipped in English in 0.56.0.

Documentation: docs/releasing.md no longer claims that Stable tag runs ahead of what is released, and CONTRIBUTING.md says what "welcome but not actively solicited" means in practice.

Nothing needs doing on update.