feat(train): workouts' weather from Open-Meteo, through the instance (ADR 0036)

A workout with a track gets the weather over it as its page opens, once
while it has none: the hours from the one it started in to the one it
ended in, kept in its sealed payload (temperature, feels-like, humidity,
precipitation, the WMO code, the wind, its gusts and direction) and shown
under its totals with the link to Open-Meteo its licence asks for.

Train's server asks Open-Meteo in the person's place (the `weather`
endpoint), so Open-Meteo never sees their address: the place rounded to
two decimals (also on the phone), a span of at most 48 hours, the
forecast API for recent spans and the archive for older ones, for people
signed in, at most 30 requests a person a minute, nothing kept or
logged. On by default; `WEATHER=off` switches it off, and
`OPEN_METEO_API_KEY` moves it to the paid hosts for an instance used
commercially.

Health Connect's fingerprint leaves the weather out, so keeping it
writes nothing again. No table and no migration.

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/train/halkyon_train_flutter/lib/l10n/app_de.arb

@@ -707,5 +707,18 @@
   "strengthNextUp": "Als Nächstes: {exercise}",
   "strengthBarAndPlates": "{bar}-kg-Stange, jede Seite: {plates}",
   "strengthHandlesAndPlates": "{bar}-kg-Griffe, jede Seite: {plates}",
-  "strengthWeightShort": "{weight} kg unter dem Plan"
+  "strengthWeightShort": "{weight} kg unter dem Plan",
+  "weatherHeading": "Wetter",
+  "weatherConditions": "{conditions, select, clear{Klar} partlyCloudy{Teils bewölkt} cloudy{Bedeckt} fog{Nebel} drizzle{Nieselregen} rain{Regen} freezingRain{Gefrierender Regen} snow{Schnee} rainShowers{Schauer} snowShowers{Schneeschauer} thunderstorm{Gewitter} other{Wetter}}",
+  "weatherTemperature": "{temperature} °C",
+  "weatherTemperatureRange": "{low}–{high} °C",
+  "weatherFeelsLike": "Gefühlt {temperature} °C",
+  "weatherWind": "Wind {speed} km/h aus {direction}",
+  "weatherWindNoDirection": "Wind {speed} km/h",
+  "weatherCalm": "Kaum Wind",
+  "weatherGusts": "Böen bis {speed} km/h",
+  "weatherDirection": "{direction, select, n{Nord} ne{Nordost} e{Ost} se{Südost} s{Süd} sw{Südwest} w{West} nw{Nordwest} other{Wind}}",
+  "weatherPrecipitation": "{amount} mm Niederschlag",
+  "weatherDry": "Trocken",
+  "weatherBy": "Wetterdaten von Open-Meteo.com"
 }