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

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

frontend/tests/components/home/HeroSection.test.tsx

@@ -100,7 +100,7 @@ describe('HeroSection', () => {
     );
 
     const githubLink = screen.getByRole('link', { name: /view on github/i });
-    expect(githubLink).toHaveAttribute('href', 'https://github.com/your-org/fast-next-template');
+    expect(githubLink).toHaveAttribute('href', 'https://gitea.pragmazest.com/cardosofelipe/syndarix');
     expect(githubLink).toHaveAttribute('target', '_blank');
     expect(githubLink).toHaveAttribute('rel', 'noopener noreferrer');
   });