修复 weeks/anchorIndex remember 缓存失效

weeks = days.chunked(7) 每帧创建新列表导致 remember key 变化、缓存失效。
将 weeks 包裹在 remember(days) 中，anchorIndex 缓存才能正确生效。

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

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

@@ -62,7 +62,7 @@ fun CalendarMonthPage(
     }
     val density = LocalDensity.current
 
-    val weeks = days.chunked(7)
+    val weeks = remember(days) { days.chunked(7) }
     val anchorIndex = remember(weeks, selectedDate) {
         weeks.indexOfFirst { week -> week.any { it.date == selectedDate } }
     }