feat(emergency): searchExpert接口返回ConDoctor专家数据 + 修复IM UserSig缓存key未区分secretKey的问题

1. searchExpert新增ConDoctor专家字段:
   - 新增ConDoctorMapper直接查询qh_con_doctor表(同库,避免跨模块依赖)
   - EmergencyProfessionUser新增17个@TableField(exist=false)字段承载专家数据
   - searchExpert方法中批量查询ConDoctor并逐字段填充
   - 用户非专家时ConDoctor字段为null
   - 更新API文档-移动端接口.md

2. IM签名缓存优化:
   - TencentCloudImUtil新增secretKey注入
   - Redis key从 silence:im_user_sig:{sdkAppId}:{id}
     改为 silence:im_user_sig:{hash(sdkAppId+secretKey)}:{id}
   - 解决secretKey变更时旧缓存签名仍被命中导致IM请求失败的问题

Co-Authored-By: Claude <noreply@anthropic.com>

health-im/health-im-biz/src/main/java/com/renkang/im/util/TencentCloudImUtil.java

@@ -52,6 +52,8 @@ public class TencentCloudImUtil {
 
     @Value("${IMConfig.sdkAppId}")
     private long sdkAppId;
+    @Value("${IMConfig.secretKey}")
+    private String secretKey;
 
     @Autowired
     private TximUtil tximUtil;
@@ -73,8 +75,16 @@ public class TencentCloudImUtil {
         return System.currentTimeMillis() + "" + StrUtil.subSuf(Math.random() + "", 2);
     }
 
+    /**
+     * 获取IM配置指纹，用于区分不同配置的缓存
+     * 当 sdkAppId 或 secretKey 变更时指纹变化，旧缓存自动失效
+     */
+    private String getConfigFingerprint() {
+        return Integer.toHexString(Objects.hash(sdkAppId, secretKey));
+    }
+
     private String buildUserSigKey(String identifier) {
-        return REDIS_IM_USER_SIG_PREFIX + sdkAppId + ":" + identifier;
+        return REDIS_IM_USER_SIG_PREFIX + getConfigFingerprint() + ":" + identifier;
     }
 
     /**