perf(core): offload LunarCache precomputing and batch calculation to Dispatchers.Default

core/src/main/kotlin/plus/rua/project/CalendarViewModel.kt

@@ -3,6 +3,7 @@ package plus.rua.project
 import androidx.lifecycle.ViewModel
 import androidx.lifecycle.viewModelScope
 import kotlinx.coroutines.launch
+import kotlinx.coroutines.Dispatchers
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.MutableStateFlow
 import kotlinx.coroutines.flow.SharingStarted
@@ -81,7 +82,7 @@ class CalendarViewModel(
             getMonthGridInfo(normalizedYear, normalizedMonth)
         }
 
-        viewModelScope.launch {
+        viewModelScope.launch(Dispatchers.Default) {
             monthsToPrecompute.forEach { info ->
                 val dates = (0 until info.totalDays).map { i ->
                     info.startDate.plus(DatePeriod(days = i))

core/src/main/kotlin/plus/rua/project/ui/CalendarMonthPage.kt

@@ -33,6 +33,8 @@ import plus.rua.project.DayCellInfo
 import plus.rua.project.LunarCache
 import plus.rua.project.ShiftKind
 
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.withContext
 
 /**
  * 月度日历网格页面，支持两阶段折叠动画。
@@ -80,7 +82,9 @@ fun CalendarMonthPage(
         key1 = year,
         key2 = month
     ) {
-        value = LunarCache.default.getOrComputeBatch(days.map { it.date })
+        value = withContext(Dispatchers.Default) {
+            LunarCache.default.getOrComputeBatch(days.map { it.date })
+        }
     }
 
     val holidayEdges = remember(lunarDataMap, year, month) {