v0.55.0: m Use the widget's line icons for sky conditions on the web pages

The web pages showed emoji for sky conditions while the widget uses its own
line icons. The glance page and the hourly tables (/day, /tomorrow,
/weekend, /hourly) now render the widget's ic_cond_*.xml vector drawables
as inline SVG in the text colour; the glance header's icon uses the accent,
like the widget's hero.

condition_icons.go holds the path data; TestConditionIconsMatchWidget reads
the Android XML and fails if the two copies drift. Clear and partly cloudy
hours after dark show the moon and plain cloud, as on the widget. The
stylesheet version and service-worker caches are bumped so installed PWAs
load the new CSS.