feat: add PowerShell installer for Windows, improve shell installer

- install.ps1: native Windows installer via PowerShell
  irm .../install.ps1 | iex
  Installs to ~/.flashduty/bin and auto-adds to user PATH
- install.sh: add PATH warning when install dir is not in PATH

Author: debidong

install.ps1

@@ -0,0 +1,100 @@
+# Flashduty CLI installer for Windows
+# Usage: irm https://raw.githubusercontent.com/flashcatcloud/flashduty-cli/main/install.ps1 | iex
+#
+# Environment variables:
+#   FLASHDUTY_VERSION     - specific version to install (e.g. "v0.1.2")
+#   FLASHDUTY_INSTALL_DIR - install directory (default: $HOME\.flashduty\bin)
+
+$ErrorActionPreference = "Stop"
+
+$Repo = "flashcatcloud/flashduty-cli"
+$Binary = "flashduty-cli.exe"
+$InstalledName = "flashduty.exe"
+
+function Write-Info($msg) {
+    Write-Host "[flashduty] $msg"
+}
+
+function Fail($msg) {
+    Write-Error "[flashduty] $msg"
+    exit 1
+}
+
+# --- detect architecture ---
+
+function Get-Arch {
+    switch ($env:PROCESSOR_ARCHITECTURE) {
+        "AMD64" { return "x86_64" }
+        "ARM64" { return "arm64" }
+        default  { Fail "unsupported architecture: $env:PROCESSOR_ARCHITECTURE" }
+    }
+}
+
+# --- resolve version ---
+
+function Get-Version {
+    if ($env:FLASHDUTY_VERSION) {
+        return $env:FLASHDUTY_VERSION
+    }
+    try {
+        $release = Invoke-RestMethod -Uri "https://api.github.com/repos/$Repo/releases/latest" -UseBasicParsing
+        return $release.tag_name
+    } catch {
+        Fail "could not determine latest version. Set FLASHDUTY_VERSION to install a specific version."
+    }
+}
+
+# --- main ---
+
+$Arch = Get-Arch
+$Version = Get-Version
+
+$InstallDir = if ($env:FLASHDUTY_INSTALL_DIR) {
+    $env:FLASHDUTY_INSTALL_DIR
+} else {
+    Join-Path $HOME ".flashduty\bin"
+}
+
+$Archive = "flashduty-cli_Windows_${Arch}.zip"
+$Url = "https://github.com/$Repo/releases/download/$Version/$Archive"
+
+Write-Info "Installing Flashduty CLI $Version (Windows/$Arch)"
+Write-Info "Downloading $Url"
+
+$TmpDir = Join-Path ([System.IO.Path]::GetTempPath()) "flashduty-install-$([System.Guid]::NewGuid().ToString('N'))"
+New-Item -ItemType Directory -Path $TmpDir -Force | Out-Null
+
+try {
+    $ArchivePath = Join-Path $TmpDir $Archive
+    [Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
+    Invoke-WebRequest -Uri $Url -OutFile $ArchivePath -UseBasicParsing
+
+    Expand-Archive -Path $ArchivePath -DestinationPath $TmpDir -Force
+
+    $BinaryPath = Join-Path $TmpDir $Binary
+    if (-not (Test-Path $BinaryPath)) {
+        Fail "binary '$Binary' not found in archive"
+    }
+
+    # Create install directory
+    if (-not (Test-Path $InstallDir)) {
+        New-Item -ItemType Directory -Path $InstallDir -Force | Out-Null
+    }
+
+    $DestPath = Join-Path $InstallDir $InstalledName
+    Move-Item -Path $BinaryPath -Destination $DestPath -Force
+
+    Write-Info "Installed to $DestPath"
+
+    # Add to user PATH if not already there
+    $UserPath = [Environment]::GetEnvironmentVariable("Path", "User")
+    if ($UserPath -notlike "*$InstallDir*") {
+        [Environment]::SetEnvironmentVariable("Path", "$UserPath;$InstallDir", "User")
+        $env:Path = "$env:Path;$InstallDir"
+        Write-Info "Added $InstallDir to user PATH (restart your terminal for it to take effect)"
+    }
+
+    Write-Info "Run 'flashduty version' to verify"
+} finally {
+    Remove-Item -Path $TmpDir -Recurse -Force -ErrorAction SilentlyContinue
+}

install.sh

@@ -114,6 +114,14 @@ main() {
     chmod +x "${INSTALL_DIR}/${INSTALLED_NAME}"
 
     info "Installed to ${INSTALL_DIR}/${INSTALLED_NAME}"
+
+    # Warn if install dir is not in PATH
+    case ":${PATH}:" in
+        *":${INSTALL_DIR}:"*) ;;
+        *) info "WARNING: ${INSTALL_DIR} is not in your PATH. Add it with:"
+           info "  export PATH=\"${INSTALL_DIR}:\$PATH\"" ;;
+    esac
+
     info "Run 'flashduty version' to verify"
 }