fix(aiot): snap端点改用302重定向到COS公共URL

<img>标签请求snap时，直接302重定向到COS公共URL，
浏览器自动跟随重定向加载图片。用sendRedirect绕过
GlobalResponseAdvice的WVPResult包装，避免byte[]类型转换错误。
同时GlobalResponseAdvice增加byte[]排除以防其他场景。

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

src/main/java/com/genersoft/iot/vmp/aiot/controller/AiRoiController.java

@@ -15,6 +15,8 @@ import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
 import org.springframework.web.bind.annotation.*;
 
+import jakarta.servlet.http.HttpServletResponse;
+import java.io.IOException;
 import java.util.List;
 import java.util.Map;
 
@@ -88,22 +90,21 @@ public class AiRoiController {
     public ResponseEntity<?> getSnap(
             @RequestParam String cameraCode,
             @RequestParam(defaultValue = "false") boolean force,
-            @RequestHeader(value = "Accept", defaultValue = "application/json") String accept) {
+            @RequestHeader(value = "Accept", defaultValue = "application/json") String accept,
+            HttpServletResponse httpResponse) throws IOException {
 
         Map<String, Object> result = screenshotService.requestScreenshot(cameraCode, force);
 
-        // 如果是 <img> 标签发起的请求（Accept: image/*），直接返回图片字节
+        // <img> 标签请求（Accept: image/*）：302 重定向到 COS 公共 URL
         if (accept.contains("image/") && "ok".equals(result.get("status"))) {
-            byte[] image = screenshotService.proxyScreenshotImage(cameraCode);
-            if (image != null) {
-                return ResponseEntity.ok()
-                        .contentType(MediaType.IMAGE_JPEG)
-                        .header("Cache-Control", "max-age=60")
-                        .body(image);
+            String cosUrl = (String) result.get("url");
+            if (cosUrl != null && cosUrl.startsWith("https://")) {
+                httpResponse.sendRedirect(cosUrl);
+                return null;
             }
         }
 
-        // 默认返回 JSON（XHR/fetch 请求）
+        // JSON 请求（XHR/fetch）：返回 JSON
         return ResponseEntity.ok(result);
     }