refactor: 改进 CameraHelper 资源清理的错误处理

- 添加 stopRepeating() 和 abortCaptures() 调用
- 为每个资源关闭操作添加独立的 try-catch
- 确保即使部分资源关闭失败，其他资源仍会被清理

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

android-app/app/src/main/java/com/usbwebcam/CameraHelper.kt

@@ -149,11 +149,32 @@ class CameraHelper(
     }
 
     private fun closeCamera() {
+        try {
+            captureSession?.stopRepeating()
+            captureSession?.abortCaptures()
+        } catch (e: Exception) {
+            e.printStackTrace()
+        }
+
+        try {
             captureSession?.close()
+        } catch (e: Exception) {
+            e.printStackTrace()
+        }
         captureSession = null
+
+        try {
             imageReader?.close()
+        } catch (e: Exception) {
+            e.printStackTrace()
+        }
         imageReader = null
+
+        try {
             cameraDevice?.close()
+        } catch (e: Exception) {
+            e.printStackTrace()
+        }
         cameraDevice = null
     }
 }