fix: 二维码静默区2格+圆角8%，防止裁切定位角

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

app/src/main/java/com/xiaoqu/watch/ui/bind/BindFragment.kt

@@ -73,7 +73,7 @@ class BindFragment : BaseFragment<FragmentBindBinding>() {
             // ZXing 生成二维码 Bitmap（缩小静默区，让二维码更大）
             val size = 500
             val hints = hashMapOf<com.google.zxing.EncodeHintType, Any>(
-                com.google.zxing.EncodeHintType.MARGIN to 0  // 去掉静默区，圆角裁剪才对称
+                com.google.zxing.EncodeHintType.MARGIN to 2  // 保留 2 格静默区，防止圆角裁掉定位角
             )
             val bitMatrix: BitMatrix = MultiFormatWriter().encode(
                 qrData, BarcodeFormat.QR_CODE, size, size, hints
@@ -108,7 +108,7 @@ class BindFragment : BaseFragment<FragmentBindBinding>() {
         val canvas = android.graphics.Canvas(output)
         val paint = android.graphics.Paint(android.graphics.Paint.ANTI_ALIAS_FLAG)
         val rect = android.graphics.RectF(0f, 0f, width.toFloat(), height.toFloat())
-        val radius = width * 0.12f
+        val radius = width * 0.08f  // 8% 圆角，避免裁到二维码定位角
         canvas.drawRoundRect(rect, radius, radius, paint)
         paint.xfermode = android.graphics.PorterDuffXfermode(android.graphics.PorterDuff.Mode.SRC_IN)
         canvas.drawBitmap(squareBitmap, 0f, 0f, paint)