Fix manual switch reverting instantly, add weather forecast

- scheduler: "Show X now" was a true one-shot -- reverted on the very next
  5s tick, causing the flash-to-X-then-flash-back-to-clock behavior. Now
  pins for 5 minutes (still preemptable by Navidrome priority, which stays
  authoritative). Added a "Resume automatic" action/button and status
  display showing what's pinned and until when.
- weather: daily forecast strip (3/5/7 days, selectable in settings) below
  current conditions, via Open-Meteo's daily= params in the same request.
  Fixed a bad symbol choice along the way -- DejaVu Sans has no glyph for
  the partly-cloudy emoji, was rendering as a tofu box; swapped to the
  plain cloud symbol, verified glyph coverage for the whole WMO code table.

web/templates/settings_weather.html

@@ -19,6 +19,18 @@
     </div>
   </div>
 
+  <div class="card">
+    <div class="section-label">Forecast</div>
+    <div class="field">
+      <label for="forecast_days">Days to show</label>
+      <select id="forecast_days" name="forecast_days">
+        <option value="3" {{ "selected" if settings.forecast_days == 3 or not settings.forecast_days }}>3 days</option>
+        <option value="5" {{ "selected" if settings.forecast_days == 5 }}>5 days</option>
+        <option value="7" {{ "selected" if settings.forecast_days == 7 }}>7 days</option>
+      </select>
+    </div>
+  </div>
+
   <div class="card">
     <div class="section-label">Or enter coordinates manually</div>
     <p class="hint" style="margin: -0.25rem 0 1rem;">Leave the city field above empty to use these instead.</p>