修复ROI截图：改用ZLM内部RTSP地址，解决ffmpeg无法直连摄像头源的问题

后端改用app/stream参数构建ZLM内部地址(rtsp://127.0.0.1:{port}/{app}/{stream})，
避免ffmpeg从Docker内直接连接摄像头RTSP源。增加47255字节默认logo检测。
前端同步更新snap URL构建方式。

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

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

@@ -91,14 +91,23 @@ public class AiRoiController {
     @Operation(summary = "获取摄像头截图")
     @GetMapping("/snap")
     public void getSnap(HttpServletResponse resp,
-                        @RequestParam String url) {
+                        @RequestParam String app,
+                        @RequestParam String stream) {
         MediaServer mediaServer = mediaServerService.getDefaultMediaServer();
         if (mediaServer == null) {
             log.warn("[AI截图] 无可用媒体服务器");
             resp.setStatus(HttpServletResponse.SC_SERVICE_UNAVAILABLE);
             return;
         }
-        // 直接调用ZLM的getSnap同步接口，传入RTSP源地址
+        // 使用ZLM内部RTSP流地址截图（流必须在线）
+        String internalUrl;
+        if (mediaServer.getRtspPort() != 0) {
+            internalUrl = String.format("rtsp://127.0.0.1:%s/%s/%s", mediaServer.getRtspPort(), app, stream);
+        } else {
+            internalUrl = String.format("http://127.0.0.1:%s/%s/%s.live.mp4", mediaServer.getHttpPort(), app, stream);
+        }
+        log.info("[AI截图] app={}, stream={}, 内部地址={}", app, stream, internalUrl);
+
         String zlmApi = String.format("http://%s:%s/index/api/getSnap",
                 mediaServer.getIp(), mediaServer.getHttpPort());
         HttpUrl httpUrl = HttpUrl.parse(zlmApi);
@@ -108,14 +117,14 @@ public class AiRoiController {
         }
         HttpUrl requestUrl = httpUrl.newBuilder()
                 .addQueryParameter("secret", mediaServer.getSecret())
-                .addQueryParameter("url", url)
-                .addQueryParameter("timeout_sec", "15")
+                .addQueryParameter("url", internalUrl)
+                .addQueryParameter("timeout_sec", "10")
                 .addQueryParameter("expire_sec", "1")
                 .build();
 
         OkHttpClient client = new OkHttpClient.Builder()
                 .connectTimeout(5, TimeUnit.SECONDS)
-                .readTimeout(20, TimeUnit.SECONDS)
+                .readTimeout(15, TimeUnit.SECONDS)
                 .build();
 
         try {
@@ -123,14 +132,14 @@ public class AiRoiController {
             Response response = client.newCall(request).execute();
             if (response.isSuccessful() && response.body() != null) {
                 String contentType = response.header("Content-Type", "");
-                if (contentType.contains("image")) {
+                byte[] bytes = response.body().bytes();
+                // ZLM默认logo是47255字节，跳过它
+                if (contentType.contains("image") && bytes.length != 47255) {
                     resp.setContentType(MediaType.IMAGE_JPEG_VALUE);
-                    byte[] bytes = response.body().bytes();
                     resp.getOutputStream().write(bytes);
                     resp.getOutputStream().flush();
                 } else {
-                    // ZLM返回的是JSON错误信息，不是图片
-                    log.warn("[AI截图] ZLM未返回图片，可能流未在线: {}", response.body().string());
+                    log.warn("[AI截图] 截图返回默认logo或非图片，流可能未在线，size={}", bytes.length);
                     resp.setStatus(HttpServletResponse.SC_NO_CONTENT);
                 }
             } else {