feat: compose Android app and verify native calendar and reminders

scripts/build-android.ps1

@@ -0,0 +1,15 @@
+param([string]$ToolchainRoot = 'C:/Users/david/Desktop/app/.tools')
+$ErrorActionPreference = 'Stop'
+$env:HEPAN_TOOLCHAIN_ROOT=$ToolchainRoot
+. "$PSScriptRoot/android-env.ps1"
+$projectRoot=Split-Path $PSScriptRoot -Parent
+Push-Location "$projectRoot/mobile"
+try {
+    flutter.bat build apk --debug
+    if($LASTEXITCODE -ne 0) { throw 'Android 构建失败，未复制 APK' }
+    $built=Join-Path (Get-Location) 'build/app/outputs/flutter-apk/app-debug.apk'
+    if(!(Test-Path -LiteralPath $built)) { throw '本次构建未生成 APK' }
+    New-Item -ItemType Directory -Force "$projectRoot/dist" | Out-Null
+    Copy-Item -LiteralPath $built -Destination "$projectRoot/dist/hepan-everyday-debug.apk" -Force
+    Get-Item -LiteralPath "$projectRoot/dist/hepan-everyday-debug.apk" | Select-Object FullName,Length,LastWriteTime
+} finally { Pop-Location }