fix(调度): 完善粘性会话清理与账号调度刷新

- Update/BulkUpdate 按不可调度字段触发缓存刷新
- GatewayCache 支持多前缀会话键清理
- 模型路由与混合调度优化粘性会话处理
- 补充调度与缓存相关测试覆盖

backend/internal/service/sticky_session_test.go

@@ -0,0 +1,54 @@
+//go:build unit
+
+// Package service 提供 API 网关核心服务。
+// 本文件包含 shouldClearStickySession 函数的单元测试，
+// 验证粘性会话清理逻辑在各种账号状态下的正确行为。
+//
+// This file contains unit tests for the shouldClearStickySession function,
+// verifying correct sticky session clearing behavior under various account states.
+package service
+
+import (
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+)
+
+// TestShouldClearStickySession 测试粘性会话清理判断逻辑。
+// 验证在以下情况下是否正确判断需要清理粘性会话：
+//   - nil 账号：不清理（返回 false）
+//   - 状态为错误或禁用：清理
+//   - 不可调度：清理
+//   - 临时不可调度且未过期：清理
+//   - 临时不可调度已过期：不清理
+//   - 正常可调度状态：不清理
+//
+// TestShouldClearStickySession tests the sticky session clearing logic.
+// Verifies correct behavior for various account states including:
+// nil account, error/disabled status, unschedulable, temporary unschedulable.
+func TestShouldClearStickySession(t *testing.T) {
+	now := time.Now()
+	future := now.Add(1 * time.Hour)
+	past := now.Add(-1 * time.Hour)
+
+	tests := []struct {
+		name    string
+		account *Account
+		want    bool
+	}{
+		{name: "nil account", account: nil, want: false},
+		{name: "status error", account: &Account{Status: StatusError, Schedulable: true}, want: true},
+		{name: "status disabled", account: &Account{Status: StatusDisabled, Schedulable: true}, want: true},
+		{name: "schedulable false", account: &Account{Status: StatusActive, Schedulable: false}, want: true},
+		{name: "temp unschedulable", account: &Account{Status: StatusActive, Schedulable: true, TempUnschedulableUntil: &future}, want: true},
+		{name: "temp unschedulable expired", account: &Account{Status: StatusActive, Schedulable: true, TempUnschedulableUntil: &past}, want: false},
+		{name: "active schedulable", account: &Account{Status: StatusActive, Schedulable: true}, want: false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			require.Equal(t, tt.want, shouldClearStickySession(tt.account))
+		})
+	}
+}