feat: 添加 USB 摄像头连接功能

- 新增 Android USB 摄像头 APP (MJPEG 服务器)
- 电脑端支持 ADB 端口转发连接
- 修复 .gitignore 忽略 Android 文件

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

android-app/.idea/appInsightsSettings.xml

@@ -0,0 +1,26 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="AppInsightsSettings">
+    <option name="tabSettings">
+      <map>
+        <entry key="Firebase Crashlytics">
+          <value>
+            <InsightsFilterSettings>
+              <option name="connection">
+                <ConnectionSetting>
+                  <option name="appId" value="PLACEHOLDER" />
+                  <option name="mobileSdkAppId" value="" />
+                  <option name="projectId" value="" />
+                  <option name="projectNumber" value="" />
+                </ConnectionSetting>
+              </option>
+              <option name="signal" value="SIGNAL_UNSPECIFIED" />
+              <option name="timeIntervalDays" value="THIRTY_DAYS" />
+              <option name="visibilityType" value="ALL" />
+            </InsightsFilterSettings>
+          </value>
+        </entry>
+      </map>
+    </option>
+  </component>
+</project>