Fix stale day/night weather glyph (derive at render time)

[shining-cat]

Problem

The weather glyph showed a moon crescent during the day (observed at 13:44). nowIsDay was baked once at fetch time from Open-Meteo's is_day, cached as a boolean, and merely read back on every minute-tick redraw. Weather refreshes at most every 30 min (network-constrained, Doze-deferrable), so the day/night flag froze between fetches — the moon persisted into daytime and vice-versa.

Fix

Fetch and cache today's sunrise/sunset, and derive nowIsDay at render time from the current clock instead of trusting the stale cached boolean. Self-corrects every minute-tick even with zero daytime fetches (Doze-proof).

• daily=weather_code,sunrise,sunset on the fetch → DailyDto (sunrise/sunset defaulted to emptyList(), so a custom endpoint that omits them still parses) → carried on WeatherSnapshot → cached with two new nullable string keys (remove-on-null; no migration — old caches read null).
• New pure DayNightResolver.isDay(now, sunriseIso, sunsetIso, fallback) — time-of-day compare over [sunrise, sunset); falls back to the fetch-time is_day when times are absent or unparseable.
• WidgetStateResolver applies it using its already-injected now lambda, copy()-correcting the snapshot. DotGrid is untouched — the renderer stays a dumb consumer.

Time-of-day comparison (not date-matched) is immune to a missed-midnight cache and is plenty precise for a sun-vs-moon glyph.

Tests

TDD, JUnit5 + injected-lambda clock + hand fakes:

• new DayNightResolverTest (9) — window, inclusive-sunrise/exclusive-sunset boundaries, null/unparseable fallback, and the 13:44-moon regression.
• WidgetStateResolverTest — stale is_day=false snapshot corrected to day at render; fallback kept when sunrise/sunset absent.
• WeatherMapperTest, ForecastDtoParseTest, DataStorePersistenceTest extended for sunrise/sunset mapping, parsing (incl. omitted), and cache round-trip (incl. null).

./gradlew test spotlessCheck — all green.

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