Add confirmation dialogs to destructive SaveManager and ThemeManager actions

[corradedied]

Destructive and irreversible actions (overwrite, delete, reset) in SaveManager and ThemeManager previously executed immediately on click with no confirmation step, making accidental data loss easy.

Window:AddDialog is now used to gate these actions behind a Cancel (Ghost) & action (Destructive) prompt:

• ThemeManager: Create theme (name collision only), Overwrite theme, Delete theme, Reset default theme

• SaveManager: Create config (name collision only), Overwrite config, Delete config, Reset autoload config

For Create theme/config, the dialog only appears when the entered name already exists — a silent overwrite would otherwise occur. For all other destructive buttons, the dialog always appears.

Library.Window is now stored on the Library object at the end of CreateWindow so addons can reach AddDialog via self.Library.Window without requiring a separate reference to be passed in.

Screenshots

ThemeManager

SaveManager