Feature/v2/right rail (#4255)

# Description of Changes

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Please provide a summary of the changes, including:

- What was changed
- Why the change was made
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Closes #(issue_number)
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---

## Checklist

### General

- [ ] I have read the [Contribution
Guidelines](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/CONTRIBUTING.md)
- [ ] I have read the [Stirling-PDF Developer
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md)
(if applicable)
- [ ] I have read the [How to add new languages to
Stirling-PDF](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md)
(if applicable)
- [ ] I have performed a self-review of my own code
- [ ] My changes generate no new warnings

### Documentation

- [ ] I have updated relevant docs on [Stirling-PDF's doc
repo](https://github.com/Stirling-Tools/Stirling-Tools.github.io/blob/main/docs/)
(if functionality has heavily changed)
- [ ] I have read the section [Add New Translation
Tags](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/HowToAddNewLanguage.md#add-new-translation-tags)
(for new translation tags only)

### UI Changes (if applicable)

- [ ] Screenshots or videos demonstrating the UI changes are attached
(e.g., as comments or direct attachments in the PR)

### Testing (if applicable)

- [ ] I have tested my changes locally. Refer to the [Testing
Guide](https://github.com/Stirling-Tools/Stirling-PDF/blob/main/devGuide/DeveloperGuide.md#6-testing)
for more details.

---------

Co-authored-by: ConnorYoh <[email protected]>
Co-authored-by: Anthony Stirling <[email protected]>

frontend/src/types/rightRail.ts

@@ -0,0 +1,26 @@
+import React from 'react';
+
+export type RightRailSection = 'top' | 'middle' | 'bottom';
+
+export interface RightRailButtonConfig {
+	/** Unique id for the button, also used to bind action callbacks */
+	id: string;
+	/** Icon element to render */
+	icon: React.ReactNode;
+	/** Tooltip content (can be localized node) */
+	tooltip: React.ReactNode;
+	/** Optional ARIA label for a11y (separate from visual tooltip) */
+	ariaLabel?: string;
+	/** Optional i18n key carried by config */
+	templateKey?: string;
+	/** Visual grouping lane */
+	section?: RightRailSection;
+	/** Sorting within a section (lower first); ties broken by id */
+	order?: number;
+	/** Initial disabled state */
+	disabled?: boolean;
+	/** Initial visibility */
+	visible?: boolean;
+}
+
+export type RightRailAction = () => void;