feat: add shadcn admin workspace

start-admin.ps1

@@ -0,0 +1,33 @@
+param(
+  [switch]$Install
+)
+
+$ErrorActionPreference = "Stop"
+
+$repoRoot = Split-Path -Parent $MyInvocation.MyCommand.Path
+$adminDir = Join-Path $repoRoot "admin"
+
+if (-not (Test-Path $adminDir)) {
+  throw "Admin directory not found: $adminDir"
+}
+
+Push-Location $adminDir
+
+try {
+  if ($Install -or -not (Test-Path (Join-Path $adminDir "node_modules"))) {
+    Write-Host "[admin] Installing dependencies..." -ForegroundColor Cyan
+    npm install
+    if ($LASTEXITCODE -ne 0) {
+      throw "npm install failed"
+    }
+  }
+
+  Write-Host "[admin] Starting Vite admin workspace..." -ForegroundColor Green
+  npm run dev
+  if ($LASTEXITCODE -ne 0) {
+    throw "npm run dev failed"
+  }
+}
+finally {
+  Pop-Location
+}