fix(app): poster — date-only text, left-aligned title/time/venue (QR stays centered)

用户反馈：海报日期仍带时间（表单已日期粒度，海报 formatAlbumDateTime 同步改
posterDate 只显 y/M/d）；宣传图下标题/时间/地址居左；二维码保持居中。

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

apps/mobile/lib/pages/share_qr_dialog.dart

@@ -379,18 +379,16 @@ class _PosterSheetState extends ConsumerState<_PosterSheet> {
     final localeName = l10n.localeName;
     final url = shareAlbumUrl(widget.album, localeName);
     final title = albumDisplayTitle(widget.album, localeName);
-    final start = formatAlbumDateTime(
+    // 海报日期：日期粒度（UI06 选择器已去时间；展示同口径）。
-      widget.album.startAt,
+    String posterDate(DateTime utc) {
-      widget.album.timezone,
+      final wall = tryToAlbumZone(utc, widget.album.timezone) ?? utc.toUtc();
-      localeName,
+      return '${wall.year}/${wall.month}/${wall.day}';
-    );
+    }
+
+    final start = posterDate(widget.album.startAt);
     final end = widget.album.endAt == null
         ? null
-        : formatAlbumDateTime(
+        : posterDate(widget.album.endAt!);
-            widget.album.endAt!,
-            widget.album.timezone,
-            localeName,
-          );
     final dateRange = end == null ? start : '$start ~ $end';
     final venue = albumDisplayVenue(widget.album, localeName);
     String? addressForPoster(AlbumSummary album) {
@@ -451,19 +449,19 @@ class _PosterSheetState extends ConsumerState<_PosterSheet> {
                         padding: const EdgeInsets.all(kSpace24),
                         child: Column(
                           children: [
-                            // 活动标题。
+                            // 活动标题（居左；二维码保持居中）。
                             Text(
                               title,
-                              textAlign: TextAlign.center,
+                              textAlign: TextAlign.left,
                               style: theme.textTheme.titleLarge?.copyWith(
                                 color: const Color(0xFF172033),
                                 fontWeight: FontWeight.w700,
                               ),
                             ),
                             const SizedBox(height: kSpace12),
-                            // 时间。
+                            // 时间（居左）。
                             Row(
-                              mainAxisAlignment: MainAxisAlignment.center,
+                              mainAxisAlignment: MainAxisAlignment.start,
                               children: [
                                 Icon(
                                   Icons.event_outlined,
@@ -486,7 +484,7 @@ class _PosterSheetState extends ConsumerState<_PosterSheet> {
                             if (venue != null) ...[
                               const SizedBox(height: kSpace4),
                               Row(
-                                mainAxisAlignment: MainAxisAlignment.center,
+                                mainAxisAlignment: MainAxisAlignment.start,
                                 children: [
                                   Icon(
                                     Icons.place_outlined,

apps/mobile/test/pages/share_qr_page_test.dart

@@ -81,7 +81,8 @@ void main() {
     expect(find.byType(QrImageView), findsOneWidget);
     expect(find.text('Scan to view photos'), findsOneWidget);
     expect(find.text('Download poster image'), findsOneWidget);
-    expect(find.text('2026/9/18 14:30'), findsOneWidget);
+    // UI06：海报日期粒度（无时间）。
+    expect(find.text('2026/9/18'), findsOneWidget);
   });
 
   testWidgets('Copy link（主操作）→ 剪贴板收到带 lang 的 URL + 已复制提示',