fix(billing): 重排任务复用钱包预留

平台额度跨窗口重排时保留任务已有的钱包预留，后续 Worker 领取复用同一幂等键，避免重复 reserve/release 事务。\n\n补齐排队任务取消后的原子结算释放，并允许任务 attempt 持久化软负载、满载原因和选择原因等有界路由快照。\n\n验证：go test ./...；go vet ./...；钱包预留复用与排队取消 PostgreSQL 集成测试。

apps/api/internal/runner/service.go

@@ -730,6 +730,12 @@ func (s *Service) executeWithToken(ctx context.Context, task store.GatewayTask,
 	var firstPreprocessing parameterPreprocessingLog
 	var walletReservations []store.WalletBillingReservation
 	walletReservationFinalized := false
+	retainWalletReservationForQueue := func() {
+		// A queued task still owns its billing hold. Keeping the same active
+		// reservation lets the next Worker claim reuse its idempotency key
+		// instead of emitting another reserve/release pair.
+		walletReservationFinalized = true
+	}
 	defer func() {
 		if !walletReservationFinalized && len(walletReservations) > 0 {
 			_ = s.store.ReleaseTaskBillingReservations(context.WithoutCancel(ctx), walletReservations, "task_not_settled")
@@ -844,6 +850,7 @@ candidatesLoop:
 					if queueErr != nil {
 						return Result{}, queueErr
 					}
+					retainWalletReservationForQueue()
 					return Result{Task: queued, Output: queued.Result}, &TaskQueuedError{Delay: delay}
 				}
 				return Result{}, admissionErr
@@ -1098,6 +1105,7 @@ candidatesLoop:
 					if queueErr != nil {
 						return Result{}, queueErr
 					}
+					retainWalletReservationForQueue()
 					return Result{Task: queued, Output: queued.Result}, &TaskQueuedError{Delay: delay}
 				}
 				attemptNo = s.recordFailedAttempt(ctx, failedAttemptRecord{
@@ -1222,6 +1230,7 @@ candidatesLoop:
 		if queueErr != nil {
 			return Result{}, queueErr
 		}
+		retainWalletReservationForQueue()
 		return Result{Task: queued, Output: queued.Result}, &TaskQueuedError{Delay: 0}
 	}
 	if task.AsyncMode && errors.Is(lastErr, store.ErrRateLimited) && store.RateLimitRetryable(lastErr) {
@@ -1232,6 +1241,7 @@ candidatesLoop:
 		if queueErr != nil {
 			return Result{}, queueErr
 		}
+		retainWalletReservationForQueue()
 		return Result{Task: queued, Output: queued.Result}, &TaskQueuedError{Delay: delay}
 	}
 	extraMetrics := []map[string]any{}