docs: Update architecture for supabase

test: Add tests for auth workflow

app/utils/auth.ts

@@ -0,0 +1,14 @@
+export const PUBLIC_ROUTES = ['/', '/login', '/signup', '/auth/callback'] as const
+
+/**
+ * Pure auth decision logic — no Nuxt/Supabase dependencies.
+ * Returns the path to redirect to, or null if no redirect is needed.
+ */
+export function checkAuthRedirect(
+  userValue: { id: string } | null,
+  path: string,
+): string | null {
+  if ((PUBLIC_ROUTES as readonly string[]).includes(path)) return null
+  if (!userValue) return '/'
+  return null
+}