Replace "FastNext" branding with "PragmaStack" across the project

- Updated all references, metadata, and templates to reflect the new branding, including layout files, components, and documentation.
- Replaced hardcoded color tokens like `green-600` with semantic tokens (`success`, `warning`, etc.) for improved design consistency.
- Enhanced `globals.css` with new color tokens for success, warning, and destructive states using the OKLCH color model.
- Added comprehensive branding guidelines and updated the design system documentation to align with the new identity.
- Updated tests and mocks to reflect the branding changes and ensured all visual/verbal references match "PragmaStack".
- Added new `branding/README.md` and `branding` docs for mission, values, and visual identity definition.

frontend/src/app/[locale]/demos/page.tsx

@@ -26,9 +26,9 @@ import { Badge } from '@/components/ui/badge';
 import { Separator } from '@/components/ui/separator';
 
 export const metadata: Metadata = {
-  title: 'Demo Tour | FastNext Template',
+  title: 'Demo Tour | PragmaStack',
   description:
-    'Try all features with demo credentials - comprehensive guide to the FastNext template',
+    'Try all features with demo credentials - comprehensive guide to the PragmaStack',
 };
 
 const demoCategories = [