feat: 添加联系我们配置接口和字典配置缓存

1. 新增DictionaryItem字典配置结构体
2. 添加字典配置缓存及失效逻辑
3. 实现联系我们接口的业务逻辑和测试用例
4. 注册联系我们API路由
5. 集成字典配置到admin内部客户端
6. 处理字典配置更新的kafka事件

server/kafka_config_events.go

@@ -92,6 +92,9 @@ func executeKafkaConfigEvent(envelope kafkaEnvelope) error {
 		}
 	case configEventDictionaryUpdated, configEventThirdPartyUpdated:
 		store.InvalidateThirdPartyConfigCache(payload.Group)
+		if strings.TrimSpace(envelope.EventType) == configEventDictionaryUpdated {
+			store.InvalidateDictionaryConfigCache(payload.Group)
+		}
 		if payload.Group == "moderation" {
 			store.InvalidateModerationConfigCache(tenantCode, true, false, false)
 		}