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/home/Header.test.tsx

@@ -37,7 +37,7 @@ describe('Header', () => {
       />
     );
 
-    expect(screen.getByText('FastNext')).toBeInTheDocument();
+    expect(screen.getByText('PragmaStack')).toBeInTheDocument();
     expect(screen.getByText('Template')).toBeInTheDocument();
   });
 
@@ -50,7 +50,7 @@ describe('Header', () => {
       />
     );
 
-    const logoLink = screen.getByRole('link', { name: /fastnext template/i });
+    const logoLink = screen.getByRole('link', { name: /pragmastack template/i });
     expect(logoLink).toHaveAttribute('href', '/');
   });