feat: weather card — precip probability %, condition text, unit-aware wind

- Fetch precipitation_probability_max from Open-Meteo (replaces precip_sum
  in the card display — probability is more useful at a glance than mm)
- Show WMO condition description text on each forecast day
- Convert wind speed to mph when temp unit is F; pass wind_unit in response
- Display 💧 X% chance of rain; 💨 X mph/km/h wind per day

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/WeatherCard.vue

@@ -6,7 +6,7 @@ interface ForecastDay {
   condition: string
   high: number
   low: number
-  precip_mm: number
+  precip_probability: number | null
   windspeed_max: number
 }
 
@@ -19,6 +19,7 @@ interface WeatherData {
   today_low: number | null
   yesterday_high: number | null
   yesterday_low: number | null
+  wind_unit?: string
   forecast: ForecastDay[]
 }
 
@@ -87,10 +88,11 @@ const fetchedAtLabel = computed(() => {
       <div v-for="day in weather.forecast" :key="day.day" class="weather-forecast-day">
         <span class="forecast-day-name">{{ day.day }}</span>
         <span class="forecast-icon">{{ weatherIcon(day.condition) }}</span>
+        <span class="forecast-condition">{{ day.condition }}</span>
         <span class="forecast-temps">{{ day.high }}° / {{ day.low }}°</span>
-        <span v-if="day.precip_mm > 0" class="forecast-precip">💧 {{ day.precip_mm }}mm</span>
-        <span v-else class="forecast-precip forecast-precip--dry">—</span>
-        <span class="forecast-wind">💨 {{ day.windspeed_max }}km/h</span>
+        <span v-if="day.precip_probability != null && day.precip_probability > 0" class="forecast-precip">💧 {{ day.precip_probability }}%</span>
+        <span v-else class="forecast-precip forecast-precip--dry">💧 —</span>
+        <span class="forecast-wind">💨 {{ day.windspeed_max }} {{ weather.wind_unit ?? 'km/h' }}</span>
       </div>
     </div>
   </div>
@@ -186,6 +188,14 @@ const fetchedAtLabel = computed(() => {
   line-height: 1;
 }
 
+.forecast-condition {
+  font-size: 0.7rem;
+  color: var(--color-text-muted);
+  text-align: center;
+  line-height: 1.2;
+  word-break: break-word;
+}
+
 .forecast-temps {
   white-space: nowrap;
 }