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]/admin/layout.tsx

@@ -12,7 +12,7 @@ import { AdminSidebar, Breadcrumbs } from '@/components/admin';
 
 export const metadata: Metadata = {
   title: {
-    template: '%s | Admin | FastNext Template',
+    template: '%s | Admin | PragmaStack',
     default: 'Admin Dashboard',
   },
 };