灯泡、报警灯改用自绘 SVG，删除教材配套资料中的图片

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/public/devices/alarm-off.svg

@@ -0,0 +1,20 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="150" height="150" viewBox="0 0 150 150">
+  <defs>
+    <linearGradient id="dome" x1="0" x2="1">
+      <stop offset="0" stop-color="#8e3b3b"/>
+      <stop offset="0.4" stop-color="#c46a6a"/>
+      <stop offset="1" stop-color="#6e2a2a"/>
+    </linearGradient>
+    <linearGradient id="base" x1="0" x2="0" y1="0" y2="1">
+      <stop offset="0" stop-color="#4b4f56"/>
+      <stop offset="1" stop-color="#2c2f34"/>
+    </linearGradient>
+  </defs>
+  <!-- 灯罩 -->
+  <path d="M40 112V70a35 35 0 0 1 70 0v42z" fill="url(#dome)" stroke="#5a2222" stroke-width="2"/>
+  <path d="M52 74a23 23 0 0 1 16-22" fill="none" stroke="#e8b4b4" stroke-width="5" stroke-linecap="round" opacity="0.6"/>
+  <rect x="60" y="72" width="30" height="34" rx="4" fill="#7a3030" opacity="0.6"/>
+  <!-- 底座 -->
+  <rect x="30" y="112" width="90" height="16" rx="4" fill="url(#base)"/>
+  <rect x="24" y="128" width="102" height="10" rx="3" fill="#222428"/>
+</svg>