fix(auth): resolve middleware Edge Runtime + layout redirect loop

Two bugs:
1. auth.ts imported postgres (Node.js TCP) which crashes in Edge Runtime,
   causing Auth.js to silently fall back to redirecting all requests to login.
   Fix: split into auth.config.ts (Edge-safe, no DB) used by middleware,
   and auth.ts (full, with DB) used by server components.

2. /agent/layout.tsx applied to /agent/login, so unauthenticated login page
   visits redirected to themselves in an infinite loop.
   Fix: moved dashboard + layout into (protected) route group so login page
   has no auth layout.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

teressa-copeland-homes/src/app/agent/(protected)/dashboard/page.tsx

@@ -0,0 +1,17 @@
+import { auth } from "@/lib/auth";
+import { redirect } from "next/navigation";
+
+export default async function DashboardPage() {
+  // Defense-in-depth session check (layout also checks, this is belt-and-suspenders)
+  const session = await auth();
+  if (!session) redirect("/agent/login");
+
+  return (
+    <div>
+      <h1 className="text-2xl font-semibold text-gray-900">Dashboard</h1>
+      <p className="mt-2 text-gray-500">
+        Welcome back, {session.user?.email}. Portal content coming in Phase 3.
+      </p>
+    </div>
+  );
+}

teressa-copeland-homes/src/app/agent/(protected)/layout.tsx

@@ -0,0 +1,26 @@
+import { auth } from "@/lib/auth";
+import { redirect } from "next/navigation";
+import { LogoutButton } from "@/components/ui/LogoutButton";
+
+export default async function AgentLayout({
+  children,
+}: {
+  children: React.ReactNode;
+}) {
+  // Defense-in-depth: middleware handles most cases, this catches edge cases
+  const session = await auth();
+  if (!session) redirect("/agent/login");
+
+  return (
+    <div className="min-h-screen bg-gray-50">
+      <header className="bg-white border-b border-gray-200 px-6 py-4 flex items-center justify-between">
+        <span className="text-sm font-medium text-gray-700">Agent Portal</span>
+        <div className="flex items-center gap-4">
+          <span className="text-sm text-gray-500">{session.user?.email}</span>
+          <LogoutButton />
+        </div>
+      </header>
+      <main className="p-6">{children}</main>
+    </div>
+  );
+}