fix(frontend): guard redirect callback against undefined url during SSG

cannamanage-frontend/src/lib/auth.ts

@@ -106,10 +106,16 @@ export const { handlers, signIn, signOut, auth } = NextAuth({
       return session
     },
     async redirect({ url, baseUrl }) {
+      // Guard: url may be undefined during static generation
+      if (!url) return baseUrl
       // Handle relative URLs
       if (url.startsWith("/")) return `${baseUrl}${url}`
       // Handle same-origin URLs
-      if (new URL(url).origin === baseUrl) return url
+      try {
+        if (new URL(url).origin === baseUrl) return url
+      } catch {
+        // Invalid URL — fall back to baseUrl
+      }
       return baseUrl
     },
   },