Feature/toasts and error handling (#4496)

# Description of Changes

- Added error handling and toast notifications

---

## 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/theme/mantineTheme.ts

@@ -14,6 +14,32 @@ const primary: MantineColorsTuple = [
   'var(--color-primary-900)',
 ];
 
+const green: MantineColorsTuple = [
+  'var(--color-green-50)',
+  'var(--color-green-100)',
+  'var(--color-green-200)',
+  'var(--color-green-300)',
+  'var(--color-green-400)',
+  'var(--color-green-500)',
+  'var(--color-green-600)',
+  'var(--color-green-700)',
+  'var(--color-green-800)',
+  'var(--color-green-900)',
+];
+
+const yellow: MantineColorsTuple = [
+  'var(--color-yellow-50)',
+  'var(--color-yellow-100)',
+  'var(--color-yellow-200)',
+  'var(--color-yellow-300)',
+  'var(--color-yellow-400)',
+  'var(--color-yellow-500)',
+  'var(--color-yellow-600)',
+  'var(--color-yellow-700)',
+  'var(--color-yellow-800)',
+  'var(--color-yellow-900)',
+];
+
 const gray: MantineColorsTuple = [
   'var(--color-gray-50)',
   'var(--color-gray-100)',
@@ -34,6 +60,8 @@ export const mantineTheme = createTheme({
   // Color palette
   colors: {
     primary,
+    green,
+    yellow,
     gray,
   },