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/Header.test.tsx

@@ -55,7 +55,7 @@ describe('Header', () => {
       />
     );
 
-    expect(screen.getByText('PragmaStack')).toBeInTheDocument();
+    expect(screen.getByText('Syndarix')).toBeInTheDocument();
   });
 
   it('logo links to homepage', () => {
@@ -67,7 +67,7 @@ describe('Header', () => {
       />
     );
 
-    const logoLink = screen.getByRole('link', { name: /PragmaStack/i });
+    const logoLink = screen.getByRole('link', { name: /Syndarix/i });
     expect(logoLink).toHaveAttribute('href', '/');
   });
 
@@ -97,12 +97,12 @@ describe('Header', () => {
 
       const githubLinks = screen.getAllByRole('link', { name: /github/i });
       const desktopGithubLink = githubLinks.find((link) =>
-        link.getAttribute('href')?.includes('github.com')
+        link.getAttribute('href')?.includes('gitea.pragmazest.com')
       );
 
       expect(desktopGithubLink).toHaveAttribute(
         'href',
-        'https://github.com/your-org/fast-next-template'
+        'https://gitea.pragmazest.com/cardosofelipe/syndarix'
       );
       expect(desktopGithubLink).toHaveAttribute('target', '_blank');
       expect(desktopGithubLink).toHaveAttribute('rel', 'noopener noreferrer');