fix: 注册 TenantAwareLoadBalancer 为 Spring Bean

问题：TenantAwareLoadBalancer 类存在但未被注册为 Spring Bean

解决方案：
1. 创建 TenantLoadBalancerAutoConfig 配置类
   - @ConditionalOnProperty 启用条件配置
   - @Bean 注册 ReactorServiceInstanceLoadBalancer

2. 添加 Spring Boot 自动配置注册
   - META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports
   - 注册 TenantLoadBalancerAutoConfig、NacosMetadataConfig、MybatisTenantAutoConfig

fund-common/src/main/java/com/fundplatform/common/loadbalancer/TenantLoadBalancerAutoConfig.java

@@ -0,0 +1,44 @@
+package com.fundplatform.common.loadbalancer;
+
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.cloud.loadbalancer.core.ReactorServiceInstanceLoadBalancer;
+import org.springframework.cloud.loadbalancer.core.ServiceInstanceListSupplier;
+import org.springframework.cloud.loadbalancer.support.LoadBalancerClientFactory;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.core.env.Environment;
+
+/**
+ * 多租户负载均衡器自动配置
+ * 
+ * <p>当 tenant.routing.enabled=true 时启用租户感知的负载均衡器</p>
+ * 
+ * <p>配置示例：</p>
+ * <pre>
+ * tenant:
+ *   routing:
+ *     enabled: true
+ * </pre>
+ */
+@Configuration
+@ConditionalOnProperty(name = "tenant.routing.enabled", havingValue = "true", matchIfMissing = true)
+public class TenantLoadBalancerAutoConfig {
+    
+    /**
+     * 注册租户感知负载均衡器
+     * 
+     * <p>替换默认的 RoundRobinLoadBalancer，根据租户组路由实例</p>
+     */
+    @Bean
+    public ReactorServiceInstanceLoadBalancer tenantAwareLoadBalancer(
+            Environment environment,
+            LoadBalancerClientFactory loadBalancerClientFactory) {
+        
+        String serviceId = environment.getProperty(LoadBalancerClientFactory.PROPERTY_NAME);
+        
+        return new TenantAwareLoadBalancer(
+            serviceId,
+            loadBalancerClientFactory.getLazyProvider(serviceId, ServiceInstanceListSupplier.class)
+        );
+    }
+}

fund-common/src/main/resources/META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports

@@ -0,0 +1,3 @@
+com.fundplatform.common.loadbalancer.TenantLoadBalancerAutoConfig
+com.fundplatform.common.nacos.NacosMetadataConfig
+com.fundplatform.common.mybatis.MybatisTenantAutoConfig