修复月→年视图切换卡顿：Pager 缓存降为 0 + 移除延迟预组合

Perfetto trace 分析发现严重卡顿根因：
- MonthView→YearView 切换耗时 2435ms
- Choreographer#doFrame 单帧超时 4288ms
- compose📟cache_window:keepAroundItems 阻塞 554ms×2
- Compose:onForgotten 组件销毁 600ms

修复：
1. CalendarPager/WeekPager/年视图 Pager 的 beyondViewportPageCount 从 1→0
   月视图缓存页从 3 页(126 DayCell)降至 1 页(42 DayCell)
2. 移除 yearPagerBeyondViewport 延迟预组合机制（不再需要）

shared/src/commonMain/kotlin/plus/rua/project/ui/CalendarMonthView.kt

@@ -51,7 +51,6 @@ import androidx.compose.ui.input.pointer.pointerInput
 import androidx.compose.ui.layout.onSizeChanged
 import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.unit.dp
-import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.launch
 import kotlinx.datetime.DatePeriod
 import kotlinx.datetime.LocalDate
@@ -93,24 +92,11 @@ fun CalendarMonthView(
     var screenHeightPx by remember { mutableIntStateOf(0) }
     var calendarContentHeightPx by remember { mutableIntStateOf(0) }
     var isMenuExpanded by remember { mutableStateOf(false) }
-    var yearPagerBeyondViewport by remember { mutableStateOf(0) }
-
     // 视图切换时自动关闭菜单
     LaunchedEffect(viewModel.isYearView) {
         isMenuExpanded = false
     }
 
-    // 年视图动画完成后再恢复预组合，避免动画期间触发邻页组合阻塞帧
-    LaunchedEffect(viewModel.isYearView) {
-        if (viewModel.isYearView) {
-            snapshotFlow { viewModel.yearViewProgress }
-                .first { it >= 1f }
-            yearPagerBeyondViewport = 1
-        } else {
-            yearPagerBeyondViewport = 0
-        }
-    }
-
     val pagerState = rememberPagerState(initialPage = START_PAGE, pageCount = { Int.MAX_VALUE })
 
     // 年视图分页器
@@ -364,7 +350,7 @@ fun CalendarMonthView(
                 )
                 HorizontalPager(
                     state = yearPagerState,
-                    beyondViewportPageCount = yearPagerBeyondViewport,
+                    beyondViewportPageCount = 0,
                     flingBehavior = PagerDefaults.flingBehavior(state = yearPagerState),
                     modifier = Modifier
                         .fillMaxWidth()

shared/src/commonMain/kotlin/plus/rua/project/ui/CalendarPager.kt

@@ -67,7 +67,7 @@ fun CalendarPager(
 
     HorizontalPager(
         state = pagerState,
-        beyondViewportPageCount = 1,
+        beyondViewportPageCount = 0,
         flingBehavior = PagerDefaults.flingBehavior(state = pagerState),
         modifier = modifier
     ) { page ->

shared/src/commonMain/kotlin/plus/rua/project/ui/WeekPager.kt

@@ -66,7 +66,7 @@ fun WeekPager(
 
     HorizontalPager(
         state = pagerState,
-        beyondViewportPageCount = 1,
+        beyondViewportPageCount = 0,
         flingBehavior = PagerDefaults.flingBehavior(state = pagerState),
         modifier = modifier
     ) { page ->