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/lib/i18n/metadata.test.ts

@@ -27,8 +27,8 @@ describe('metadata utilities', () => {
     });
 
     it('should have English and Italian names', () => {
-      expect(siteConfig.name.en).toBe('FastNext Template');
-      expect(siteConfig.name.it).toBe('FastNext Template');
+      expect(siteConfig.name.en).toBe('PragmaStack');
+      expect(siteConfig.name.it).toBe('PragmaStack');
     });
 
     it('should have English and Italian descriptions', () => {