fix(aiot): 改用COS公共URL+修复GlobalResponseAdvice排除byte[]

1. requestScreenshot直接返回COS公共URL（不再返回代理路径）
2. GlobalResponseAdvice排除byte[]类型响应，避免图片代理被包装成WVPResult
3. handleCallback先写缓存再complete Future（保留之前的竞态修复）

COS Bucket已开启公有读，无需签名URL，直接用公共地址即可在<img>中显示。

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/main/java/com/genersoft/iot/vmp/aiot/service/impl/AiScreenshotServiceImpl.java

@@ -56,7 +56,7 @@ public class AiScreenshotServiceImpl implements IAiScreenshotService {
                 try {
                     JSONObject cached = JSON.parseObject(cacheJson);
                     result.put("status", "ok");
-                    result.put("url", "/api/ai/roi/snap/image?cameraCode=" + cameraCode);
+                    result.put("url", cached.getString("url"));
                     result.put("cached", true);
                     log.info("[AI截图] 命中缓存: cameraCode={}", cameraCode);
                     return result;
@@ -101,7 +101,7 @@ public class AiScreenshotServiceImpl implements IAiScreenshotService {
             String status = (String) callbackData.get("status");
             result.put("status", status);
             if ("ok".equals(status)) {
-                result.put("url", "/api/ai/roi/snap/image?cameraCode=" + cameraCode);
+                result.put("url", callbackData.get("url"));
             } else {
                 result.put("message", callbackData.get("message"));
             }
@@ -115,7 +115,7 @@ public class AiScreenshotServiceImpl implements IAiScreenshotService {
                     JSONObject res = JSON.parseObject(resultJson);
                     result.put("status", res.getString("status"));
                     if ("ok".equals(res.getString("status"))) {
-                        result.put("url", "/api/ai/roi/snap/image?cameraCode=" + cameraCode);
+                        result.put("url", res.getString("url"));
                         // 降级成功，写入缓存
                         writeCache(cameraCode, res.getString("url"));
                     } else {
@@ -135,7 +135,7 @@ public class AiScreenshotServiceImpl implements IAiScreenshotService {
                 try {
                     JSONObject cached = JSON.parseObject(staleCache);
                     result.put("status", "ok");
-                    result.put("url", "/api/ai/roi/snap/image?cameraCode=" + cameraCode);
+                    result.put("url", cached.getString("url"));
                     result.put("stale", true);
                     return result;
                 } catch (Exception ignored) {

src/main/java/com/genersoft/iot/vmp/conf/GlobalResponseAdvice.java

@@ -42,6 +42,11 @@ public class GlobalResponseAdvice implements ResponseBodyAdvice<Object> {
             return body;
         }
 
+        // 排除二进制响应（如图片代理返回的 byte[]）
+        if (body instanceof byte[]) {
+            return body;
+        }
+
         if (body instanceof WVPResult) {
             return body;
         }