feat(mobile): 预种明细显示来源用户ID + 修复空待领取倒计时

1. 预种待领取/可结算明细的 memo 中追加来源用户（如"来自D26022600016的预种"）
2. 修复 pendingUsdt=0 时倒计时仍然显示的问题（pending_expire_at 未清除时兜底）

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/mobile-app/lib/core/services/wallet_service.dart

@@ -87,8 +87,10 @@ class RewardsInfo {
   }
 
   /// 计算待领取剩余时间（秒）
+  /// [2026-03-01] 当 pendingUsdt=0 时（已全部结算），倒计时无意义，返回 0
   int get pendingRemainingSeconds {
     if (pendingExpireAt == null) return 0;
+    if (pendingUsdt <= 0) return 0;
     final remaining = pendingExpireAt!.difference(DateTime.now()).inSeconds;
     return remaining > 0 ? remaining : 0;
   }

frontend/mobile-app/lib/features/profile/presentation/pages/profile_page.dart

@@ -814,7 +814,12 @@ class _ProfilePageState extends ConsumerState<ProfilePage> {
       final excludedPplOrderIds = {...pendingPplOrderIds, ...expiredPplOrderIds};
       final prePlantingSettleable = prePlantingRewards.settleableRewards
           .where((r) => !excludedPplOrderIds.contains(r.sourceOrderNo))
-          .map((r) => SettleableRewardItem(
+          .map((r) {
+            final srcAcct = r.sourceAccountSequence;
+            final memoSuffix = (srcAcct != null && srcAcct.isNotEmpty)
+                ? '：来自${srcAcct}的预种'
+                : '';
+            return SettleableRewardItem(
                 id: r.id,
                 rightType: r.rightType,
                 usdtAmount: r.usdtAmount,
@@ -823,8 +828,9 @@ class _ProfilePageState extends ConsumerState<ProfilePage> {
                 claimedAt: null,
                 sourceOrderNo: r.sourceOrderNo,
                 sourceAccountSequence: r.sourceAccountSequence,
-                memo: '[预种] ${r.memo}',
-              ))
+                memo: '[预种] ${r.memo}$memoSuffix',
+            );
+          })
           .toList();
       settleableRewards = [...settleableRewards, ...prePlantingSettleable];
       debugPrint('[ProfilePage] 预种可结算奖励: ${prePlantingSettleable.length} 条 (排除 ${pendingPplOrderIds.length} 条 PENDING, ${expiredPplOrderIds.length} 条 EXPIRED)');
@@ -833,9 +839,25 @@ class _ProfilePageState extends ConsumerState<ProfilePage> {
       // wallet-service 的 pending_rewards 表包含正常认种 + 预种的待领取记录，
       // 但 reward-service 的 /rewards/pending 已经返回了正常认种的待领取记录，
       // 所以这里只筛选预种的条目（sourceOrderId 以 PPL 开头），避免重复显示。
+      //
+      // [2026-03-01] 构建 sourceOrderNo → sourceAccountSequence 映射，
+      // 用于在待领取条目中显示来源用户ID（wallet pending_rewards 表不含此字段，
+      // 但 pre-planting/my-rewards 的分配记录中有）。
+      final pplSourceAccountMap = <String, String>{};
+      for (final r in prePlantingRewards.settleableRewards) {
+        if (r.sourceAccountSequence != null && r.sourceAccountSequence!.isNotEmpty) {
+          pplSourceAccountMap[r.sourceOrderNo] = r.sourceAccountSequence!;
+        }
+      }
       final prePlantingPending = walletPendingRewards
           .where((r) => r.isPrePlanting)
-          .map((r) => PendingRewardItem(
+          .map((r) {
+            final sourceAccount = pplSourceAccountMap[r.sourceOrderId];
+            final typeName = getAllocationTypeName(r.allocationType);
+            final memo = sourceAccount != null
+                ? '[预种] $typeName：来自${sourceAccount}的预种'
+                : '[预种] $typeName';
+            return PendingRewardItem(
                 id: 'wp-${r.id}',
                 rightType: r.allocationType,
                 usdtAmount: r.usdtAmount,
@@ -844,8 +866,10 @@ class _ProfilePageState extends ConsumerState<ProfilePage> {
                 expireAt: r.expireAt,
                 remainingTimeMs: r.expireAt.difference(DateTime.now()).inMilliseconds.clamp(0, 86400000),
                 sourceOrderNo: r.sourceOrderId,
-                memo: '[预种] ${getAllocationTypeName(r.allocationType)}',
-              ))
+                sourceAccountSequence: sourceAccount,
+                memo: memo,
+            );
+          })
           .toList();
       final mergedPendingRewards = [...pendingRewards, ...prePlantingPending];
       debugPrint('[ProfilePage] 预种待领取奖励: ${prePlantingPending.length} 条');