Fix team-mode first-run: /setup no longer bounces to /sign-in

- _auth.setup.tsx: the "owner already exists?" check ran in beforeLoad, which
  executes during SSR where fetchTeamSetupStatus's relative fetch to
  /api/team-setup fails — so it always concluded an owner existed and
  redirected to /sign-in, making the create-owner screen unreachable. Move the
  check into a client-side effect with a loading state.
- setup-status.ts: add BETTER_AUTH_URL to CHECK_ENV_VARS so /api/health stops
  falsely reporting "team mode requires BETTER_AUTH_URL" when it is set (the
  Docker preflight already saw it; only the runtime health check's env
  allowlist was missing it).

Verified locally end to end against a D1 build in AUTH_MODE=team: owner
bootstrap, self-disable + 409 on repeat, Better Auth sign-in issues a session
cookie, and get-session resolves the shared organization.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/routes/_auth.setup.tsx

@@ -1,5 +1,5 @@
-import { createFileRoute, redirect, useNavigate } from "@tanstack/react-router";
-import { useState } from "react";
+import { createFileRoute, useNavigate } from "@tanstack/react-router";
+import { useEffect, useState } from "react";
 import { AuthPageCard } from "@/client/features/auth/AuthPage";
 import {
   bootstrapTeamOwner,
@@ -7,27 +7,38 @@ import {
 } from "@/client/features/auth/teamSetup";
 import { authClient } from "@/lib/auth-client";
 
-// First-run screen for `team` mode: creates the single owner account. It
-// redirects to /sign-in the moment an owner exists, so it can't be used to add
-// more users.
+// First-run screen for `team` mode: creates the single owner account. The
+// "already has an owner?" check runs client-side (it needs a DB round trip via
+// /api/team-setup, which a server-side beforeLoad can't reach with a relative
+// URL) and redirects to /sign-in once an owner exists.
 export const Route = createFileRoute("/_auth/setup")({
-  beforeLoad: async () => {
-    const status = await fetchTeamSetupStatus();
-    if (!status.needsOwner) {
-      throw redirect({ to: "/sign-in", search: {} });
-    }
-  },
   component: SetupPage,
 });
 
 function SetupPage() {
   const navigate = useNavigate();
+  const [checking, setChecking] = useState(true);
   const [name, setName] = useState("");
   const [email, setEmail] = useState("");
   const [password, setPassword] = useState("");
   const [error, setError] = useState<string | null>(null);
   const [isSubmitting, setIsSubmitting] = useState(false);
 
+  useEffect(() => {
+    let cancelled = false;
+    void fetchTeamSetupStatus().then((status) => {
+      if (cancelled) return;
+      if (!status.needsOwner) {
+        void navigate({ to: "/sign-in", search: {} });
+        return;
+      }
+      setChecking(false);
+    });
+    return () => {
+      cancelled = true;
+    };
+  }, [navigate]);
+
   async function handleSubmit(event: React.FormEvent) {
     event.preventDefault();
     setError(null);
@@ -57,6 +68,14 @@ function SetupPage() {
     }
   }
 
+  if (checking) {
+    return (
+      <div className="flex justify-center py-10">
+        <span className="loading loading-spinner loading-md" />
+      </div>
+    );
+  }
+
   return (
     <AuthPageCard
       title="Create the owner account"

src/server/lib/setup-status.ts

@@ -27,6 +27,7 @@ const CHECK_ENV_VARS = [
   "DATAFORSEO_API_KEY",
   "GOOGLE_CLIENT_ID",
   "GOOGLE_CLIENT_SECRET",
+  "BETTER_AUTH_URL",
   "BETTER_AUTH_SECRET",
   "OPENROUTER_API_KEY",
 ] as const;