feat: 电池显示电量数值 + 充电闪电标识

1. 电池图标右侧显示"75%"电量百分比（白色60%透明度）
2. 充电中在电池壳内显示⚡闪电标识

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

app/src/main/java/com/xiaoqu/watch/ui/widget/StatusBarView.kt

@@ -47,8 +47,9 @@ class StatusBarView @JvmOverloads constructor(
         drawBluetoothDot(canvas, 8f, centerY)
         drawSignalBars(canvas, 22f, centerY)
 
-        // ===== 右侧：电池 =====
+        // ===== 右侧：电量数值 + 电池图标 =====
-        drawBattery(canvas, width - 48f, centerY)
+        val batteryTextWidth = drawBatteryText(canvas, width.toFloat(), centerY)
+        drawBattery(canvas, width - batteryTextWidth - 52f, centerY)
     }
 
     /** 绘制蓝牙状态圆点 */
@@ -77,7 +78,22 @@ class StatusBarView @JvmOverloads constructor(
         }
     }
 
-    /** 绘制电池图标（壳 + 填充条 + 凸起） */
+    /** 绘制电量百分比文字（右对齐，返回文字宽度） */
+    private fun drawBatteryText(canvas: Canvas, rightEdge: Float, centerY: Float): Float {
+        val text = "${batteryLevel}%"
+        paint.style = Paint.Style.FILL
+        paint.color = 0x99FFFFFF.toInt() // 白色 60% 透明度
+        paint.textSize = 16f
+        paint.textAlign = Paint.Align.RIGHT
+        // 垂直居中：baseLine = centerY + textHeight/2 - descent
+        val metrics = paint.fontMetrics
+        val baselineY = centerY - (metrics.ascent + metrics.descent) / 2
+        canvas.drawText(text, rightEdge - 2f, baselineY, paint)
+        paint.textAlign = Paint.Align.LEFT // 恢复默认
+        return paint.measureText(text) + 4f
+    }
+
+    /** 绘制电池图标（壳 + 填充条 + 凸起 + 充电闪电） */
     private fun drawBattery(canvas: Canvas, startX: Float, centerY: Float) {
         val shellW = 28f
         val shellH = 13f
@@ -110,6 +126,18 @@ class StatusBarView @JvmOverloads constructor(
         )
         canvas.drawRoundRect(fillRect, 2f, 2f, paint)
 
+        // 充电闪电标识（电池壳内居中）
+        if (isCharging) {
+            paint.color = colorWhite
+            paint.style = Paint.Style.FILL
+            paint.textSize = 11f
+            paint.textAlign = Paint.Align.CENTER
+            val metrics = paint.fontMetrics
+            val baselineY = centerY - (metrics.ascent + metrics.descent) / 2
+            canvas.drawText("⚡", startX + shellW / 2, baselineY, paint)
+            paint.textAlign = Paint.Align.LEFT
+        }
+
         // 电池凸起（右侧小矩形）
         paint.color = colorBorder
         val nubW = 2.5f