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/store/task_history_test.go

@@ -36,6 +36,21 @@ func TestMinimalTaskResultDropsProviderRawCopy(t *testing.T) {
 	}
 }
 
+func TestMinimalTaskAttemptMetricsKeepsBoundedRoutingSnapshot(t *testing.T) {
+	metrics := minimalTaskAttemptMetrics(map[string]any{
+		"loadMetrics":     map[string]any{"concurrent": map[string]any{"softRatio": 0.5}},
+		"fullReasons":     []any{"waiting"},
+		"selectionReason": "full_avoided",
+		"requestBody":     map[string]any{"secret": "must not persist"},
+	})
+	if metrics["loadMetrics"] == nil || metrics["fullReasons"] == nil || metrics["selectionReason"] != "full_avoided" {
+		t.Fatalf("routing snapshot was dropped: %+v", metrics)
+	}
+	if metrics["requestBody"] != nil {
+		t.Fatalf("unbounded attempt payload was retained: %+v", metrics)
+	}
+}
+
 func TestTaskEventsAreMinimalAndConsecutiveDuplicatesAreSkipped(t *testing.T) {
 	db := billingV2IntegrationStore(t)
 	ctx := context.Background()