修复：ROI Canvas 响应式对齐，精确覆盖图片内容区域

通过计算 object-fit: contain 下图片的真实渲染区域，让 Canvas 精确覆盖
图片内容而非整个容器（含黑边），解决不同屏幕/缩放下 ROI 偏移问题。

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/web-antd/src/views/aiot/device/roi/components/RoiCanvas.vue

@@ -90,12 +90,43 @@ function onImageError() {
   nextTick(() => initCanvas());
 }
 
+function getImageContentRect() {
+  const img = wrapper.value?.querySelector('img');
+  if (!img || !img.naturalWidth || !wrapper.value) {
+    return {
+      x: 0,
+      y: 0,
+      w: wrapper.value?.clientWidth ?? 0,
+      h: wrapper.value?.clientHeight ?? 0,
+    };
+  }
+  const cW = wrapper.value.clientWidth;
+  const cH = wrapper.value.clientHeight;
+  const imgRatio = img.naturalWidth / img.naturalHeight;
+  const cRatio = cW / cH;
+  let rW: number;
+  let rH: number;
+  if (imgRatio > cRatio) {
+    rW = cW;
+    rH = cW / imgRatio;
+  } else {
+    rH = cH;
+    rW = cH * imgRatio;
+  }
+  return { x: (cW - rW) / 2, y: (cH - rH) / 2, w: rW, h: rH };
+}
+
 function initCanvas() {
   if (!canvas.value || !wrapper.value) return;
-  canvasWidth = wrapper.value.clientWidth;
-  canvasHeight = wrapper.value.clientHeight;
+  const rect = getImageContentRect();
+  canvasWidth = rect.w;
+  canvasHeight = rect.h;
   canvas.value.width = canvasWidth;
   canvas.value.height = canvasHeight;
+  canvas.value.style.left = `${rect.x}px`;
+  canvas.value.style.top = `${rect.y}px`;
+  canvas.value.style.width = `${rect.w}px`;
+  canvas.value.style.height = `${rect.h}px`;
   ctx = canvas.value.getContext('2d');
   redraw();
 }
@@ -365,10 +396,6 @@ function drawPolygonInProgress() {
 
 .roi-overlay {
   position: absolute;
-  top: 0;
-  left: 0;
-  width: 100%;
-  height: 100%;
   cursor: crosshair;
 }
 </style>