revert: 回退 graphicsLayer 优化，实机 GPU 合成开销过大

graphicsLayer 创建的离屏 layer 在实体机上导致 slow draw commands 激增，
整体体验比重组更卡。回退以下改动：

- WeekRow: graphicsLayer → offset + alpha
- CalendarPager: graphicsLayer → alpha
- WeekPager: graphicsLayer → alpha
- YearGridView: graphicsLayer → alpha
- BottomCard: graphicsLayer → offset + alpha
- layoutReady: graphicsLayer → alpha

保留的优化：
- DayCell produceState 上移（42 协程 → 1 协程）
- remember 稳定化 lambda 和计算

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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

@@ -15,7 +15,8 @@ import androidx.compose.runtime.produceState
 import androidx.compose.runtime.remember
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clipToBounds
-import androidx.compose.ui.graphics.graphicsLayer
+import androidx.compose.ui.draw.alpha
+import androidx.compose.foundation.layout.offset
 import androidx.compose.ui.layout.onSizeChanged
 import androidx.compose.ui.platform.LocalDensity
 import androidx.compose.ui.unit.dp
@@ -210,10 +211,8 @@ private fun WeekRow(
                     if (isAnchor && phase1 >= 1f) Modifier.background(MaterialTheme.colorScheme.surface)
                     else Modifier
                 )
-                .graphicsLayer {
-                    translationY = yOffsetPx
-                    this.alpha = rowAlpha
-                }
+                .offset(y = with(density) { yOffsetPx.toDp() })
+                .alpha(rowAlpha)
                 .then(
                     if (weekIndex == 0 && rowHeightPx == 0) {
                         Modifier.onSizeChanged { size ->

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

@@ -29,6 +29,7 @@ import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.fillMaxSize
 import androidx.compose.foundation.layout.fillMaxWidth
 import androidx.compose.foundation.layout.height
+import androidx.compose.foundation.layout.offset
 import androidx.compose.foundation.layout.padding
 import androidx.compose.foundation.layout.size
 import androidx.compose.foundation.layout.statusBarsPadding
@@ -193,7 +194,7 @@ fun CalendarMonthView(
                         modifier = Modifier
                             .fillMaxSize()
                             .background(MaterialTheme.colorScheme.background)
-                            .graphicsLayer { alpha = if (layoutReady) 1f else 0f }
+                            .alpha(if (layoutReady) 1f else 0f)
                     ) {
                         Column(
                             modifier = Modifier
@@ -323,7 +324,7 @@ fun CalendarMonthView(
                                 },
                                 sharedTransitionScope = sharedScope,
                                 animatedVisibilityScope = this@AnimatedContent,
-                                modifier = Modifier.graphicsLayer { this.alpha = crossFadeAlpha }
+                                modifier = Modifier.alpha(crossFadeAlpha)
                             )
                         }
                     }
@@ -584,8 +585,6 @@ private fun BottomCardArea(
         animationSpec = tween(350, delayMillis = 100, easing = FastOutSlowInEasing),
         label = "bottomCardSlide"
     )
-    val slideOffsetY = with(density) { (slideProgress * 200).dp.toPx() }
-
     // 延迟一帧显示 BottomCard，避免 AnimatedGif 和 lunar 计算阻塞首帧
     var hasLoaded by remember { mutableStateOf(false) }
     LaunchedEffect(Unit) {
@@ -609,10 +608,8 @@ private fun BottomCardArea(
             onExpandDragEnd = { viewModel.onExpandDragEnd() },
             dragRangePx = dragRangePx,
             modifier = modifier
-                .graphicsLayer {
-                    translationY = slideOffsetY
-                    this.alpha = 1f - slideProgress
-                }
+                .offset(y = with(density) { (slideProgress * 200).dp })
+                .alpha(1f - slideProgress)
         )
     }
 }

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

@@ -11,7 +11,7 @@ import androidx.compose.runtime.remember
 import androidx.compose.runtime.rememberCoroutineScope
 import androidx.compose.runtime.snapshotFlow
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.graphics.graphicsLayer
+import androidx.compose.ui.draw.alpha
 import kotlinx.coroutines.flow.drop
 import kotlinx.coroutines.launch
 import kotlinx.datetime.LocalDate
@@ -117,7 +117,7 @@ fun CalendarPager(
             shiftKindAt = shiftKindAt,
             showLegalHoliday = showLegalHoliday,
             onRowHeightMeasured = onRowHeightMeasured,
-            modifier = Modifier.graphicsLayer { this.alpha = alpha }
+            modifier = Modifier.alpha(alpha)
         )
     }
 }

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

@@ -13,7 +13,7 @@ import androidx.compose.runtime.getValue
 import androidx.compose.runtime.remember
 import androidx.compose.runtime.snapshotFlow
 import androidx.compose.ui.Modifier
-import androidx.compose.ui.graphics.graphicsLayer
+import androidx.compose.ui.draw.alpha
 import androidx.compose.ui.unit.dp
 import kotlinx.coroutines.flow.drop
 import kotlinx.datetime.DatePeriod
@@ -87,7 +87,7 @@ fun WeekPager(
         val weekMonday = pageToWeekMonday(page, initialWeekMonday)
         Row(
             modifier = Modifier
-                .graphicsLayer { this.alpha = alpha }
+                .alpha(alpha)
                 .fillMaxWidth()
                 .padding(vertical = ROW_PADDING_DP.dp)
         ) {