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/docs/DEMO_MODE.md

@@ -273,7 +273,7 @@ NEXT_PUBLIC_DEMO_MODE=true npm run dev
 **1. Fork Repository**
 
 ```bash
-gh repo fork your-repo/fast-next-template
+git clone https://gitea.pragmazest.com/cardosofelipe/syndarix.git
 ```
 
 **2. Connect to Vercel**