feat(规则管理): 规则查询接口返回关联通知渠道

Motivation:
前端在展示规则详情与规则列表时，需要同时看到每条规则绑定了哪些通知渠道以及各渠道的启用状态。此前规则接口只返回规则本身，渠道绑定信息需要额外请求才能获取，增加了交互成本。本次让规则读取接口一次性携带关联渠道信息。

Changes:

* 规则模型新增 Channels 字段及渠道条目结构，包含渠道标识、名称、类型和按规则维度的启用开关
* 创建、查询单条、列表查询规则接口在返回结果时填充绑定的渠道信息，无绑定时返回空列表
* 新增批量查询规则与渠道绑定关系的数据访问能力，按规则聚合返回，避免列表场景下逐条查询
* 单个渠道数据读取失败时跳过该条目，不阻断整体结果返回

internal/store/rule.go

@@ -7,6 +7,8 @@ import (
 	"fmt"
 
 	"aiaa-notification-service/internal/model"
+
+	"github.com/jmoiron/sqlx"
 )
 
 func (s *Store) CreateRule(ctx context.Context, r *model.Rule, channelIDs []int) error {
@@ -158,6 +160,30 @@ func (s *Store) GetRuleChannels(ctx context.Context, ruleID int) ([]model.RuleCh
 	return rcs, nil
 }
 
+// ListRuleChannels maps each rule to its bound channels (regardless of enabled
+// state) and the per-rule enabled switch.
+func (s *Store) ListRuleChannels(ctx context.Context, ruleIDs []int) (map[int][]model.RuleChannel, error) {
+	result := make(map[int][]model.RuleChannel, len(ruleIDs))
+	if len(ruleIDs) == 0 {
+		return result, nil
+	}
+
+	query, args, err := sqlx.In(`SELECT id, rule_id, channel_id, enabled FROM notification_rule_channel WHERE rule_id IN (?)`, ruleIDs)
+	if err != nil {
+		return nil, fmt.Errorf("build rule channels query: %w", err)
+	}
+	query = s.DB.Rebind(query)
+
+	rcs := make([]model.RuleChannel, 0)
+	if err := s.DB.SelectContext(ctx, &rcs, query, args...); err != nil {
+		return nil, fmt.Errorf("list rule channels: %w", err)
+	}
+	for _, rc := range rcs {
+		result[rc.RuleID] = append(result[rc.RuleID], rc)
+	}
+	return result, nil
+}
+
 func (s *Store) SetRuleChannelEnabled(ctx context.Context, ruleID, channelID int, enabled bool) error {
 	v := 0
 	if enabled {