Fix chart performance issues and duplicate keys

- Memoize XAxisTick and YAxisTick renderers with useCallback
- Remove Y-axis tickCount and allowDecimals=false to prevent duplicate keys
- Add React.memo to SimulationChart with custom comparison
- Remove unnecessary sorting after isFed and remove dose actions
- Add handleActionWithoutSort for actions that don't affect order
- Prevents double state updates that caused 'every other click' freezes

src/components/day-schedule.tsx

@@ -86,6 +86,7 @@ const DaySchedule: React.FC<DayScheduleProps> = ({
   }, [scheduleSort]);
 
   // Wrap action handlers to cancel pending sorts and execute action, then sort
+  // Use this ONLY for actions that might affect dose order (like time changes)
   const handleActionWithSort = React.useCallback((dayId: string, action: () => void) => {
     // Cancel pending sort
     const pendingTimeout = pendingSorts.get(dayId);
@@ -107,6 +108,12 @@ const DaySchedule: React.FC<DayScheduleProps> = ({
     }, 50);
   }, [pendingSorts, onSortDoses]);
 
+  // Handle actions that DON'T affect dose order (no sorting needed)
+  // This prevents unnecessary double state updates and improves performance
+  const handleActionWithoutSort = React.useCallback((action: () => void) => {
+    action();
+  }, []);
+
   // Clean up pending timeouts on unmount
   React.useEffect(() => {
     return () => {
@@ -437,7 +444,7 @@ const DaySchedule: React.FC<DayScheduleProps> = ({
                       {/* Action buttons - right aligned */}
                       <div className="flex flex-nowrap items-center justify-end gap-1">
                         <IconButtonWithTooltip
-                          onClick={() => handleActionWithSort(day.id, () => onUpdateDoseField(day.id, dose.id, 'isFed', !dose.isFed))}
+                          onClick={() => handleActionWithoutSort(() => onUpdateDoseField(day.id, dose.id, 'isFed', !dose.isFed))}
                           icon={<Utensils className="h-4 w-4" />}
                           tooltip={dose.isFed ? t('doseWithFood') : t('doseFasted')}
                           size="sm"
@@ -445,7 +452,7 @@ const DaySchedule: React.FC<DayScheduleProps> = ({
                           className={`h-9 w-9 p-0 ${dose.isFed ? 'bg-orange-500 hover:bg-orange-600' : ''}`}
                         />
                         <IconButtonWithTooltip
-                          onClick={() => handleActionWithSort(day.id, () => onRemoveDose(day.id, dose.id))}
+                          onClick={() => handleActionWithoutSort(() => onRemoveDose(day.id, dose.id))}
                           icon={<Trash2 className="h-4 w-4" />}
                           tooltip={t('removeDose')}
                           size="sm"

src/components/simulation-chart.tsx

@@ -52,7 +52,7 @@ const CHART_COLORS = {
   cursor: '#6b7280'           // gray-500
 } as const;
 
-const SimulationChart = ({
+const SimulationChart = React.memo(({
   combinedProfile,
   templateProfile,
   chartView,
@@ -173,7 +173,8 @@ const SimulationChart = ({
   }, [totalHours, xTickInterval]);
 
   // Custom tick renderer for x-axis to handle 12h/24h/continuous formats and dark mode
-  const XAxisTick = (props: any) => {
+  // Memoized to prevent unnecessary re-renders
+  const XAxisTick = React.useCallback((props: any) => {
     const { x, y, payload } = props;
     const h = payload.value as number;
     let label: string;
@@ -200,17 +201,18 @@ const SimulationChart = ({
         {label}
       </text>
     );
-  };
+  }, [showDayTimeOnXAxis, isDarkTheme, t]);
 
-  // Custom tick renderre for y-axis to handle dark mode
+  // Custom tick renderer for y-axis to handle dark mode
-  const YAxisTick = (props: any) => {
+  // Memoized to prevent unnecessary re-renders
+  const YAxisTick = React.useCallback((props: any) => {
     const { x, y, payload } = props;
     return (
       <text x={x} y={y + 4} textAnchor="end" fill={isDarkTheme ? '#ccc' : '#666'}>
         {payload.value}
       </text>
     );
-  };
+  }, [isDarkTheme]);
 
   // Calculate Y-axis domain based on data and user settings
   const yAxisDomain = React.useMemo(() => {
@@ -529,9 +531,7 @@ const SimulationChart = ({
               domain={yAxisDomain as any}
               axisLine={{ stroke: isDarkTheme ? '#ccc' : '#666' }}
               tick={<YAxisTick />}
-              tickCount={16}
+              allowDecimals={true}
-              interval={0}
-              allowDecimals={false}
               allowDataOverflow={false}
             />
             <RechartsTooltip
@@ -760,6 +760,27 @@ const SimulationChart = ({
       </div>
     </div>
   );
-};
+}, (prevProps, nextProps) => {
+  // Custom comparison function to prevent unnecessary re-renders
+  // Only re-render if relevant props actually changed
+  return (
+    prevProps.combinedProfile === nextProps.combinedProfile &&
+    prevProps.templateProfile === nextProps.templateProfile &&
+    prevProps.chartView === nextProps.chartView &&
+    prevProps.showDayTimeOnXAxis === nextProps.showDayTimeOnXAxis &&
+    prevProps.showDayReferenceLines === nextProps.showDayReferenceLines &&
+    prevProps.showIntakeTimeLines === nextProps.showIntakeTimeLines &&
+    prevProps.showTherapeuticRange === nextProps.showTherapeuticRange &&
+    prevProps.therapeuticRange?.min === nextProps.therapeuticRange?.min &&
+    prevProps.therapeuticRange?.max === nextProps.therapeuticRange?.max &&
+    prevProps.simulationDays === nextProps.simulationDays &&
+    prevProps.displayedDays === nextProps.displayedDays &&
+    prevProps.yAxisMin === nextProps.yAxisMin &&
+    prevProps.yAxisMax === nextProps.yAxisMax &&
+    prevProps.days === nextProps.days
+  );
+});
+
+SimulationChart.displayName = 'SimulationChart';
 
 export default SimulationChart;