feat: complete Syndarix rebranding from PragmaStack

- Update PROJECT_NAME to Syndarix in backend config
- Update all frontend components with Syndarix branding
- Replace all GitHub URLs with Gitea Syndarix repo URLs
- Update metadata, headers, footers with new branding
- Update tests to match new URLs
- Update E2E tests for new repo references
- Preserve "Built on PragmaStack" attribution in docs

Closes #13

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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

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

@@ -14,7 +14,7 @@ import { Badge } from '@/components/ui/badge';
 import { Separator } from '@/components/ui/separator';
 
 export const metadata: Metadata = {
-  title: 'Design System Hub | PragmaStack',
+  title: 'Design System Hub | Syndarix',
   description:
     'Interactive design system demonstrations with live examples - explore components, layouts, spacing, and forms built with shadcn/ui and Tailwind CSS',
 };
@@ -90,7 +90,7 @@ export default function DesignSystemHub() {
             </div>
             <p className="text-lg text-muted-foreground">
               Interactive demonstrations, live examples, and comprehensive documentation for the
-              PragmaStack design system. Built with shadcn/ui + Tailwind CSS 4.
+              Syndarix design system. Built with shadcn/ui + Tailwind CSS 4.
             </p>
           </div>
         </div>