fix: show placeholder for zero battery

banban-mini/src/pages/device/index.tsx

@@ -41,6 +41,14 @@ function getSignalLabel(value?: number | null): string {
   return '弱'
 }
 
+function formatBatteryDisplay(value?: number | null): { text: string; showPercent: boolean } {
+  if (value === null || value === undefined) return { text: '--', showPercent: false }
+  const normalized = Number(value)
+  if (!Number.isFinite(normalized)) return { text: '--', showPercent: false }
+  if (normalized === 0) return { text: '*', showPercent: false }
+  return { text: String(normalized), showPercent: true }
+}
+
 function formatSleepRange(status: DeviceStatus | null): string {
   const start = status?.disable_time_start?.trim()
   const end = status?.disable_time_end?.trim()
@@ -284,7 +292,7 @@ export default function Device() {
   const childName = child.child_name || '未设置'
   const pageTitle = `${childName} 的伴伴`
   const batteryValue = deviceStatus?.power ?? deviceStatus?.battery_pct ?? null
-  const batteryDisplay = batteryValue === null || batteryValue === undefined ? '--' : String(batteryValue)
+  const batteryDisplay = formatBatteryDisplay(batteryValue)
   const signalLabel = getSignalLabel(deviceStatus?.signal)
   const versionLabel = deviceStatus?.version || '--'
   const coordinateLabel = formatCoordinates(deviceStatus)
@@ -307,8 +315,8 @@ export default function Device() {
         </View>
         <View className='battery-section'>
           <Text className='battery-percent'>
-            {batteryDisplay}
+            {batteryDisplay.text}
-            {batteryDisplay !== '--' && <Text className='percent'>%</Text>}
+            {batteryDisplay.showPercent && <Text className='percent'>%</Text>}
           </Text>
           <Text className='battery-label'>当前电量</Text>
         </View>