优化日历模态框，添加过去日期检查，调整今天和过去日期的样式

components/simple-calendar.tsx

@@ -155,8 +155,17 @@ export function CalendarModal({
                   date.getMonth() === selectedDate.getMonth() &&
                   date.getFullYear() === selectedDate.getFullYear();
 
-                const isToday =
-                  new Date().toDateString() === date.toDateString();
+                const isToday = today.toDateString() === date.toDateString();
+
+                // Check if date is in the past (before today)
+                const isPast =
+                  !isToday &&
+                  date <
+                    new Date(
+                      today.getFullYear(),
+                      today.getMonth(),
+                      today.getDate()
+                    );
 
                 return (
                   <Pressable
@@ -173,6 +182,8 @@ export function CalendarModal({
                     <ThemedText
                       style={[
                         styles.dayText,
+                        { color: textColor },
+                        isPast && { color: subTextColor, opacity: 0.5 },
                         isSelected && { color: "#fff", fontWeight: "bold" },
                         !isSelected && isToday && { color: Colors[theme].tint },
                       ]}