Update dark mode improvements for chart

src/components/simulation-chart.tsx

@@ -85,6 +85,26 @@ const SimulationChart = ({
     return () => window.removeEventListener('resize', updateWidth);
   }, []);
 
+  // Track current theme for chart styling
+  const [isDarkTheme, setIsDarkTheme] = React.useState(false);
+
+  React.useEffect(() => {
+    const checkTheme = () => {
+      setIsDarkTheme(document.documentElement.classList.contains('dark'));
+    };
+
+    checkTheme();
+
+    // Use MutationObserver to detect theme changes
+    const observer = new MutationObserver(checkTheme);
+    observer.observe(document.documentElement, {
+      attributes: true,
+      attributeFilter: ['class']
+    });
+
+    return () => observer.disconnect();
+  }, []);
+
   // Y-axis takes ~80px, scrollable area gets the rest
   const yAxisWidth = 80;
   const scrollableWidth = containerWidth - yAxisWidth;
@@ -161,7 +181,7 @@ const SimulationChart = ({
     return ticks;
   }, [totalHours, xTickInterval]);
 
-  // Custom tick renderer for x-axis to handle 12h/24h/continuous formats
+  // Custom tick renderer for x-axis to handle 12h/24h/continuous formats and dark mode
   const XAxisTick = (props: any) => {
     const { x, y, payload } = props;
     const h = payload.value as number;
@@ -173,7 +193,7 @@ const SimulationChart = ({
       if (hour12 === 12) {
         label = t('tickNoon');
         return (
-          <text x={x} y={y + 12} textAnchor="middle" fontStyle="italic" fill="#666">
+          <text x={x} y={y + 12} textAnchor="middle" fontStyle="italic" fill={isDarkTheme ? '#ccc' : '#666'}>
             {label}
           </text>
         );
@@ -185,12 +205,22 @@ const SimulationChart = ({
       label = `${h}`;
     }
     return (
-      <text x={x} y={y + 12} textAnchor="middle" fill="#666">
+      <text x={x} y={y + 12} textAnchor="middle" fill={isDarkTheme ? '#ccc' : '#666'}>
         {label}
       </text>
     );
   };
 
+  // Custom tick renderre for y-axis to handle dark mode
+  const YAxisTick = (props: any) => {
+    const { x, y, payload } = props;
+    return (
+      <text x={x} y={y + 4} textAnchor="end" fill={isDarkTheme ? '#ccc' : '#666'}>
+        {payload.value}
+      </text>
+    );
+  };
+
   // Calculate Y-axis domain based on data and user settings
   const yAxisDomain = React.useMemo(() => {
     const numMin = parseFloat(yAxisMin);
@@ -454,6 +484,7 @@ const SimulationChart = ({
                 dataKey="timeHours"
                 type="number"
                 domain={[0, totalHours]}
+                axisLine={{ stroke: isDarkTheme ? '#ccc' : '#666' }}
                 tick={<XAxisTick />}
                 ticks={xAxisTicks}
                 tickCount={xAxisTicks.length}
@@ -467,6 +498,8 @@ const SimulationChart = ({
               // FIXME
               //label={{ value: t('axisLabelConcentration'), angle: -90, position: 'insideLeft', style: { fontStyle: 'italic', color: '#666' } }}
               domain={yAxisDomain as any}
+              axisLine={{ stroke: isDarkTheme ? '#ccc' : '#666' }}
+              tick={<YAxisTick />}
               tickCount={16}
               interval={0}
               allowDecimals={false}
@@ -528,7 +561,9 @@ const SimulationChart = ({
               cursor={{ stroke: CHART_COLORS.cursor, strokeWidth: 1, strokeDasharray: '1 1' }}
               position={{ y: 0 }}
             />
-            <CartesianGrid strokeDasharray="1 1" xAxisId="hours" yAxisId="concentration" />
+            <CartesianGrid strokeDasharray="1 1" xAxisId="hours" yAxisId="concentration"
+                  style={{ stroke: isDarkTheme ? '#666' : '#ccc' }}
+            />
 
             {showDayReferenceLines !== false && [...Array(dispDays + 1).keys()].map(day => {
               // Determine whether to use compact day labels to avoid overlap on narrow screens