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>

web/src/api/cameraConfig.js

@@ -25,6 +25,7 @@ export function stopCamera(id) {
   })
 }
 
-export function getSnapUrl(srcUrl) {
-  return `/api/ai/roi/snap?url=${encodeURIComponent(srcUrl)}`
+export function getSnapUrl(app, stream) {
+  const base = process.env.NODE_ENV === 'development' ? process.env.VUE_APP_BASE_API : ''
+  return `${base}/api/ai/roi/snap?app=${encodeURIComponent(app)}&stream=${encodeURIComponent(stream)}`
 }

web/src/views/cameraConfig/roiConfig.vue

@@ -97,6 +97,8 @@ export default {
     return {
       cameraId: '',
       srcUrl: '',
+      app: '',
+      stream: '',
       drawMode: null,
       roiList: [],
       selectedRoiId: null,
@@ -113,10 +115,9 @@ export default {
   mounted() {
     this.cameraId = decodeURIComponent(this.$route.params.cameraId)
     this.srcUrl = this.$route.query.srcUrl || ''
-    if (this.srcUrl) {
-      const base = process.env.NODE_ENV === 'development' ? process.env.VUE_APP_BASE_API : ''
-      this.snapUrl = `${base}/api/ai/roi/snap?url=${encodeURIComponent(this.srcUrl)}`
-    }
+    this.app = this.$route.query.app || ''
+    this.stream = this.$route.query.stream || ''
+    this.buildSnapUrl()
     this.loadRois()
   },
   methods: {
@@ -145,12 +146,15 @@ export default {
     startDraw(mode) {
       this.drawMode = mode
     },
-    refreshSnap() {
-      if (this.srcUrl) {
+    buildSnapUrl() {
+      if (this.app && this.stream) {
         const base = process.env.NODE_ENV === 'development' ? process.env.VUE_APP_BASE_API : ''
-        this.snapUrl = `${base}/api/ai/roi/snap?url=${encodeURIComponent(this.srcUrl)}&t=${Date.now()}`
+        this.snapUrl = `${base}/api/ai/roi/snap?app=${encodeURIComponent(this.app)}&stream=${encodeURIComponent(this.stream)}&t=${Date.now()}`
       }
     },
+    refreshSnap() {
+      this.buildSnapUrl()
+    },
     onRoiDrawn(data) {
       this.drawMode = null
       const newRoi = {