fix: 调整追剧加号卡片顺序

docs/plans/PROGRESS.md

@@ -1240,4 +1240,5 @@ $ flutter test
 
 - 追剧保持三列网格，播放历史改为左封面右信息的单列列表，行距 16。
 - 历史卡片补充 96×128 封面、观看进度、已看百分比、继续观看和编辑删除。
+- 追剧加号卡片移到全部追剧卡片之后，空列表时仍在左上角。
 - 刷新、分页与各页独立滚动位置保持；`flutter analyze`：No issues found。

lib/pages/following/following_page.dart

@@ -269,10 +269,10 @@ class _FavoritesGrid extends StatelessWidget {
           itemCount: controller.cards.length + 1,
           empty: const SizedBox.shrink(),
           itemBuilder: (context, index) {
-            if (index == 0) {
+            if (index == controller.cards.length) {
               return FollowingAddCard(onTap: onGoHome);
             }
-            final drama = controller.cards[index - 1];
+            final drama = controller.cards[index];
             final episode = drama.episodes.isEmpty
                 ? 1
                 : drama.episodes.first.number;

test/following/following_page_test.dart

@@ -116,6 +116,12 @@ void main() {
       tester.getTopLeft(titleFinder).dx,
       tester.getTopLeft(coverFinder).dx,
     );
+    expect(
+      tester.getTopLeft(card).dx,
+      lessThan(
+        tester.getTopLeft(find.byKey(const Key('following-add-card'))).dx,
+      ),
+    );
 
     await tester.tap(find.byKey(const Key('following-edit')));
     await tester.pumpAndSettle();