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/tests/components/layout/Footer.test.tsx

@@ -20,7 +20,7 @@ describe('Footer', () => {
 
       const currentYear = new Date().getFullYear();
       expect(
-        screen.getByText(`© ${currentYear} FastNext Template. All rights reserved.`)
+        screen.getByText(`© ${currentYear} PragmaStack. All rights reserved.`)
       ).toBeInTheDocument();
     });