Fix week number baseline alignment and collapsed state today jump

- MonthHeader: align week number text baseline with month text (Bottom)
- WeekPager: scroll to selectedDate's week when it changes externally,
  fixing the case where clicking "back to today" in collapsed state
  didn't navigate the week pager to the current week

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

@@ -41,7 +41,7 @@ fun MonthHeader(
             .fillMaxWidth()
             .padding(vertical = 14.dp, horizontal = 12.dp)
             .then(if (onClick != null) Modifier.clickable(onClick = onClick) else Modifier),
-        verticalAlignment = Alignment.CenterVertically
+        verticalAlignment = Alignment.Bottom
     ) {
         AnimatedContent(
             targetState = Pair(year, month),

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

@@ -16,6 +16,7 @@ import androidx.compose.ui.unit.dp
 import kotlinx.coroutines.flow.drop
 import kotlinx.datetime.DatePeriod
 import kotlinx.datetime.LocalDate
+import kotlinx.datetime.daysUntil
 import kotlinx.datetime.plus
 import kotlin.math.abs
 
@@ -42,6 +43,15 @@ fun WeekPager(
         pageCount = { Int.MAX_VALUE }
     )
 
+    // selectedDate 外部变更（如点击回到今天）时，滚动到对应周
+    LaunchedEffect(selectedDate) {
+        val targetMonday = selectedDate.toWeekMonday()
+        val targetPage = START_PAGE + (initialWeekMonday.daysUntil(targetMonday) / 7)
+        if (pagerState.currentPage != targetPage) {
+            pagerState.animateScrollToPage(targetPage)
+        }
+    }
+
     LaunchedEffect(pagerState) {
         snapshotFlow { pagerState.settledPage }.drop(1).collect { page ->
             val weekMonday = pageToWeekMonday(page, initialWeekMonday)