dayplan toolbar polish + weather archive fallback

- weather: add archive API branch in getWeather for past dates
  (previously returned no_forecast, making the day-strip widget show "—")
- dayplan: add expand/collapse-all toggle between ICS and Undo with
  animated icon swap (ChevronsUpDown <-> ChevronsDownUp)
- dayplan: drop the trip title + date range block from the sidebar header
  (already shown in the page header), toolbar now right-aligned

server/src/services/weatherService.ts

@@ -194,6 +194,37 @@ async function _getWeatherImpl(
       }
     }
 
+    // Past date: use archive API for the actual date
+    if (diffDays < -1) {
+      const dateStr = targetDate.toISOString().slice(0, 10);
+      const url = `https://archive-api.open-meteo.com/v1/archive?latitude=${lat}&longitude=${lng}&start_date=${dateStr}&end_date=${dateStr}&daily=temperature_2m_max,temperature_2m_min,weathercode,precipitation_sum&timezone=auto`;
+      const response = await fetch(url);
+      const data = await response.json() as OpenMeteoForecast;
+
+      if (!response.ok || data.error) {
+        throw new ApiError(response.status || 500, data.reason || 'Open-Meteo Archive API error');
+      }
+
+      const daily = data.daily;
+      if (daily && daily.time && daily.time.length > 0 && daily.temperature_2m_max[0] != null) {
+        const code = daily.weathercode?.[0];
+        const descriptions = lang === 'de' ? WMO_DESCRIPTION_DE : WMO_DESCRIPTION_EN;
+        const tMax = daily.temperature_2m_max[0];
+        const tMin = daily.temperature_2m_min[0];
+        const result: WeatherResult = {
+          temp: Math.round((tMax + tMin) / 2),
+          temp_max: Math.round(tMax),
+          temp_min: Math.round(tMin),
+          main: WMO_MAP[code!] || estimateCondition((tMax + tMin) / 2, daily.precipitation_sum?.[0] || 0),
+          description: descriptions[code!] || '',
+          type: 'forecast',
+        };
+        setCache(ck, result, TTL_CLIMATE_MS);
+        return result;
+      }
+      return { temp: 0, main: '', description: '', type: '', error: 'no_forecast' };
+    }
+
     // Climate / archive fallback (far-future dates)
     if (diffDays > -1) {
       const month = targetDate.getMonth() + 1;