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/components/home/PhilosophySection.tsx

@@ -33,7 +33,7 @@ export function PhilosophySection() {
           viewport={{ once: true, margin: '-100px' }}
           transition={{ duration: 0.6 }}
         >
-          <h2 className="text-3xl md:text-4xl font-bold mb-6">Why PragmaStack?</h2>
+          <h2 className="text-3xl md:text-4xl font-bold mb-6">Why Syndarix?</h2>
           <div className="space-y-4 text-lg text-muted-foreground leading-relaxed">
             <p>
               We built this template after rebuilding the same authentication, authorization, and