feat: PPT按钮预览

[AstrZero]

No description provided.

[augmentcode]

🤖 Augment PR Summary

Summary: This PR adds a dedicated “PPT 翻页按钮预览” flow to configure and preview PPT page-flip navigation bars.

Changes:

• Refactors PPTUIManager to read per-position settings (page number visibility, opacity, black background theme) from PowerPointSettings.
• Adds new persisted settings fields for each bar position (LS/RS/LB/RB) with lazy fallback to legacy PPTSButtonsOption/PPTBButtonsOption.
• Introduces PPTPageFlipPreviewWindow (fullscreen, non-activating) to visually preview all four navigation bars.
• Adds PPTPageFlipPreviewPage to edit enabled state, page number, theme, offset, opacity, and global scale with real-time preview.
• Simplifies the existing PowerPoint settings page by replacing the old per-position expander UI with a single entry card that navigates to the new preview page.
• Registers the new page in SettingsWindow navigation and adjusts pane display mode while previewing.
• Adds a minimal package.json (Express/CORS) to the repo root.

Technical Notes: Preview mode temporarily forces PPT presentation UI state, disables AvoidFullScreenHelper, and blocks MainWindow input while the Settings window stays focused.

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[augmentcode]

Review completed. 1 suggestion posted.

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[augmentcode]

Ink Canvas/Windows/SettingsViews/Pages/PowerPointPage.xaml still has Visibility bindings referencing CardShowPPTButton later in the file (e.g., around line ~110), but CardShowPPTButton was deleted in this PR; that dangling ElementName will likely cause a XAML load/binding error when the page is created.

Severity: high

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