Fix weather icons, forecast temps, and update docs

- Replace emoji weather icons with OWM icon images to fix rendering
  issues on Linux displays (e.g. ⛅ showing as a rectangle)
- Fix forecast daily max/min to use true high/low across all 3-hour
  slots instead of just the first entry of the day
- Update README: correct BACKGROUND interval (60 min), update kiosk
  setup for labwc/Wayland, add restart-calendar.sh instructions

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

static/js/app.js

@@ -7,18 +7,11 @@ const INTERVALS = {
     JOKE: 3600000           // 1 hour
 };
 
-// Weather icon mapping (OpenWeatherMap icons to emoji or text)
-const WEATHER_ICONS = {
-    '01d': '☀️', '01n': '🌙',
-    '02d': '⛅', '02n': '☁️',
-    '03d': '☁️', '03n': '☁️',
-    '04d': '☁️', '04n': '☁️',
-    '09d': '🌧️', '09n': '🌧️',
-    '10d': '🌦️', '10n': '🌧️',
-    '11d': '⛈️', '11n': '⛈️',
-    '13d': '❄️', '13n': '❄️',
-    '50d': '🌫️', '50n': '🌫️'
-};
+// Return an OWM icon image tag for a given icon code
+function weatherIcon(code) {
+    const src = `https://openweathermap.org/img/wn/${code}@2x.png`;
+    return `<img src="${src}" alt="${code}" class="owm-icon">`;
+}
 
 // Initialize the application
 document.addEventListener('DOMContentLoaded', () => {
@@ -69,7 +62,7 @@ async function updateWeather() {
         const { current, forecast } = data;
 
         document.getElementById('current-temp').textContent = `${current.temp}°`;
-        document.getElementById('weather-icon').textContent = WEATHER_ICONS[current.icon] || '🌤️';
+        document.getElementById('weather-icon').innerHTML = weatherIcon(current.icon);
 
         // Update 3-day forecast in header
         const headerForecast = document.getElementById('header-forecast');
@@ -80,7 +73,7 @@ async function updateWeather() {
             dayElement.className = 'forecast-item';
             dayElement.innerHTML = `
                 <div class="weather-label">${day.date}</div>
-                <div class="forecast-icon">${WEATHER_ICONS[day.icon] || '🌤️'}</div>
+                <div class="forecast-icon">${weatherIcon(day.icon)}</div>
                 <div class="forecast-temps">
                     <span class="high">${day.temp_max}°</span>
                     <span class="low">${day.temp_min}°</span>