fix(admin): AuthGen $y 类型修复 — [int]$y 防止 PS2EXE Object[] 降级

PS2EXE 编译后 $y 被隐式当作 Object[], 导致 $y - 2 算术运算失败:
"Method invocation failed because [System.Object[]] does not contain
a method named 'op_Subtraction'"

修复: 强类型声明 [int]$y = 72

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

admin-authcode-gui.ps1

@@ -60,7 +60,7 @@ $titleLabel.ForeColor = [System.Drawing.Color]::White
 $header.Controls.Add($titleLabel)
 
 # ─── 输入区 ───────────────────────────────────────────
-$y = 72
+[int]$y = 72
 
 # 用户名
 $lblUser = New-Object System.Windows.Forms.Label