feat(todo): the weather: a forecast on days, tasks tied to it, the days that fit (ADR 0033, D40)

A task can need weather: dry, sunny, calm and a temperature range (not
freezing, warm, or from and to as typed), set from Weather in its
details (a chip beside Priority, then a row of its own once it needs
any) and kept in its sealed payload (`weather`, schema stays 1).
Where its day's forecast misses any of it, its row carries a mark and
its details say what is missing; nothing moves and its reminder stays.
Its date picker lists the coming days the forecast fits, at its time or
from 8:00 to 20:00 without one.

The forecast is for the place set in Settings' new Weather card, kept in
the sealed settings; else, for a task with a place, its first place. The
device's location is never read for it. `ForecastCubit` asks the
instance for each place (`InstanceWeather`, rounded to about a
kilometre) as it comes, as the app opens, hourly and on a pull, and
holds the answers in memory alone. With a place in Settings, each day's
heading in Today and Upcoming shows its sky and temperatures, the 3-day
grid its icon. Settings says where the instance gives no forecasts, and
credits Open-Meteo as its licence asks.

Whats-New: A task can need dry, sunny, calm or mild weather: it is marked when the forecast doesn't fit, and its date picker shows the days that do; days show the forecast for the place set in Settings.
Whats-New-De: Eine Aufgabe kann trockenes, sonniges, windstilles oder mildes Wetter brauchen: Sie wird markiert, wenn die Vorhersage nicht passt, und ihre Datumsauswahl zeigt die passenden Tage; die Tage zeigen die Vorhersage für den Ort aus den Einstellungen.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/todo/halkyon_todo_flutter/test/support/fake_weather.dart

@@ -0,0 +1,21 @@
+import 'package:halkyon_todo_flutter/src/feature/location/data/location_reminder_gateway.dart';
+import 'package:halkyon_todo_flutter/src/feature/weather/data/weather_gateway.dart';
+import 'package:halkyon_todo_flutter/src/feature/weather/model/forecast.dart';
+
+/// Forecasts as the instance would give them (ADR 0033, D40): the hours
+/// [forecasts] holds for a place, none for one it doesn't (refused); and
+/// each place asked for.
+class FakeWeather() implements WeatherGateway {
+  final forecasts = <LatLon, List<ForecastHour>>{};
+  final asked = <LatLon>[];
+  bool isOffered = true;
+
+  @override
+  Future<bool> offered() async => isOffered;
+
+  @override
+  Future<List<ForecastHour>> forecast(LatLon place) async {
+    asked.add(place);
+    return forecasts[place] ?? (throw const WeatherUnavailable());
+  }
+}