fix: OAuth login path — /api/v1/oauth/:provider (pas auth/oauth)

frontend/src/pages/LoginPage.tsx

@@ -91,7 +91,7 @@ export default function LoginPage() {
           {PROVIDERS.map(({ id, label }) => (
             <a
               key={id}
-              href={`${base}/api/v1/auth/oauth/${id}?redirectUrl=${redirectUrl}`}
+              href={`${base}/api/v1/oauth/${id}?redirectUrl=${redirectUrl}`}
               className="flex items-center justify-center rounded border border-od-border bg-od-surface px-4 py-2.5 text-sm text-od-muted transition-colors hover:border-od-accent hover:text-od-accent"
             >
               {label}