fix: 重写圆角二维码渲染

- 使用独立 Paint 对象，修复颜色问题
- 模块大小固定 16px，圆角 35%
- 白色圆角背景 + 黑色圆角模块
- 模块间 10% 缝隙

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

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

@@ -88,30 +88,15 @@ class BindFragment : BaseFragment<FragmentBindBinding>() {
 
     /**
      * 将 ZXing BitMatrix 转换为圆角风格二维码 Bitmap
-     * 每个模块（小方块）都是圆角矩形，整体图片也是圆角
+     * 每个模块（小方块）都是圆角矩形，白色背景带圆角
      */
     private fun bitMatrixToBitmap(matrix: BitMatrix): Bitmap {
-        val width = matrix.width
-        val height = matrix.height
-        val outputSize = 500  // 输出图片尺寸
-
-        val bitmap = Bitmap.createBitmap(outputSize, outputSize, Bitmap.Config.ARGB_8888)
-        val canvas = android.graphics.Canvas(bitmap)
-        val paint = android.graphics.Paint(android.graphics.Paint.ANTI_ALIAS_FLAG)
-
-        // 白色背景（圆角）
-        paint.color = 0xFFFFFFFF.toInt()
-        val bgRadius = outputSize * 0.08f
-        canvas.drawRoundRect(
-            android.graphics.RectF(0f, 0f, outputSize.toFloat(), outputSize.toFloat()),
-            bgRadius, bgRadius, paint
-        )
-
-        // 计算每个模块的尺寸和偏移
-        // 找到二维码实际内容的边界（去掉 ZXing 的空白边距）
-        var left = width; var top = height; var right = 0; var bottom = 0
-        for (y in 0 until height) {
-            for (x in 0 until width) {
+        // 找到二维码实际内容边界（去掉 ZXing 空白边距）
+        val w = matrix.width
+        val h = matrix.height
+        var left = w; var top = h; var right = 0; var bottom = 0
+        for (y in 0 until h) {
+            for (x in 0 until w) {
                 if (matrix[x, y]) {
                     if (x < left) left = x
                     if (x > right) right = x
@@ -120,32 +105,53 @@ class BindFragment : BaseFragment<FragmentBindBinding>() {
                 }
             }
         }
-        val qrWidth = right - left + 1
-        val qrHeight = bottom - top + 1
+        val qrCols = right - left + 1
+        val qrRows = bottom - top + 1
 
-        // 留出内边距
-        val padding = outputSize * 0.06f
-        val drawArea = outputSize - padding * 2
-        val moduleSize = drawArea / maxOf(qrWidth, qrHeight)
-        val offsetX = padding + (drawArea - qrWidth * moduleSize) / 2
-        val offsetY = padding + (drawArea - qrHeight * moduleSize) / 2
+        // 输出参数
+        val moduleSize = 16f          // 每个模块像素大小
+        val padding = moduleSize * 2  // 内边距
+        val outputSize = (maxOf(qrCols, qrRows) * moduleSize + padding * 2).toInt()
 
-        // 绘制每个黑色模块为圆角矩形
-        paint.color = 0xFF000000.toInt()
-        val moduleRadius = moduleSize * 0.3f  // 每个模块 30% 圆角
-        val gap = moduleSize * 0.08f  // 模块间留小缝隙
+        val bitmap = Bitmap.createBitmap(outputSize, outputSize, Bitmap.Config.ARGB_8888)
+        val canvas = android.graphics.Canvas(bitmap)
 
-        for (y in top..bottom) {
-            for (x in left..right) {
-                if (matrix[x, y]) {
-                    val px = offsetX + (x - left) * moduleSize + gap
-                    val py = offsetY + (y - top) * moduleSize + gap
-                    val rect = android.graphics.RectF(
-                        px, py,
-                        px + moduleSize - gap * 2,
-                        py + moduleSize - gap * 2
+        // 白色圆角背景
+        val bgPaint = android.graphics.Paint(android.graphics.Paint.ANTI_ALIAS_FLAG).apply {
+            color = 0xFFFFFFFF.toInt()
+            style = android.graphics.Paint.Style.FILL
+        }
+        val bgRadius = outputSize * 0.08f
+        canvas.drawRoundRect(
+            android.graphics.RectF(0f, 0f, outputSize.toFloat(), outputSize.toFloat()),
+            bgRadius, bgRadius, bgPaint
+        )
+
+        // 黑色模块画笔
+        val modulePaint = android.graphics.Paint(android.graphics.Paint.ANTI_ALIAS_FLAG).apply {
+            color = 0xFF000000.toInt()
+            style = android.graphics.Paint.Style.FILL
+        }
+
+        // 居中偏移
+        val offsetX = padding + (maxOf(qrCols, qrRows) - qrCols) * moduleSize / 2
+        val offsetY = padding + (maxOf(qrCols, qrRows) - qrRows) * moduleSize / 2
+
+        // 模块圆角和缝隙
+        val cornerRadius = moduleSize * 0.35f
+        val inset = moduleSize * 0.1f
+
+        // 逐个绘制圆角模块
+        for (row in 0 until qrRows) {
+            for (col in 0 until qrCols) {
+                if (matrix[left + col, top + row]) {
+                    val px = offsetX + col * moduleSize + inset
+                    val py = offsetY + row * moduleSize + inset
+                    val size = moduleSize - inset * 2
+                    canvas.drawRoundRect(
+                        android.graphics.RectF(px, py, px + size, py + size),
+                        cornerRadius, cornerRadius, modulePaint
                     )
-                    canvas.drawRoundRect(rect, moduleRadius, moduleRadius, paint)
                 }
             }
         }