Feature/v2/remove pages (#4445)

# Description of Changes

- Addition of the remove pages tool
- Addition of the remove blank pages tool

---

## 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.

frontend/src/utils/pageSelection.ts

@@ -0,0 +1,23 @@
+export const validatePageNumbers = (pageNumbers: string): boolean => {
+  if (!pageNumbers.trim()) return false;
+
+  // Normalize input for validation: remove spaces around commas and other spaces
+  const normalized = pageNumbers.replace(/\s*,\s*/g, ',').replace(/\s+/g, '');
+  const parts = normalized.split(',');
+
+  // Regular expressions for different page number formats
+  const allToken = /^all$/i; // Select all pages
+  const singlePageRegex = /^[1-9]\d*$/; // Single page: positive integers only (no 0)
+  const rangeRegex = /^[1-9]\d*-(?:[1-9]\d*)?$/; // Range: 1-5 or open range 10-
+  const mathRegex = /^(?=.*n)[0-9n+\-*/() ]+$/; // Mathematical expressions with n and allowed chars
+
+  return parts.every(part => {
+    if (!part) return false;
+    return (
+      allToken.test(part) ||
+      singlePageRegex.test(part) ||
+      rangeRegex.test(part) ||
+      mathRegex.test(part)
+    );
+  });
+};