Fixed the remaining Manager runtime coupling.

1. Root cause of the database error
The Manager proxy was bypassing installation checks, but / still resolved to src/app/page.tsx, which statically imported:
- @/auth
- Prisma
- business branding
- business permissions
- primary business data
The root route now redirects to /manager inside the proxy before the business homepage is evaluated.
2. Root cause of the Auth.js error
The global business SessionProvider was mounted around Manager pages. It automatically requested:

The business homepage is not evaluated first.
5. Provider and authentication separation
Manager mode:
- Uses ManagerProviders
- Uses the signed Manager cookie session
- Does not mount SessionProvider
- Does not call /api/auth/session
- Does not import business Auth.js or Prisma
Business mode:
- Dynamically loads the existing business Providers
- Continues using Auth.js and SessionProvider
- Preserves installation, /owner, and /staff behavior
6. Database independence
Manager mode now avoids database initialization for:
- Proxy requests
- Root metadata and viewport
- Root routing
- Manager pages
- Manager APIs
- Manifest requests
- Health requests
- Business Auth.js requests
- Business cron requests
No fake DATABASE_* variables were added.
7. Tests
Added coverage for:
- Manager / routing
- Manager /manager access
- No installation-state check in Manager mode
- Prisma import protection
- Business installation checks
- /owner protection
- Business Auth.js 404 boundary
- Manager health route without Prisma
- Manager manifest without business branding
8. Validation

src/app/api/auth/[...nextauth]/route.ts

@@ -1,3 +1,20 @@
-import { handlers } from "@/auth";
+/**
+ * Business Auth.js is intentionally unavailable in the standalone Manager
+ * deployment. Keeping this check before the dynamic import prevents a stale
+ * SessionProvider or direct request from initialising Prisma there.
+ */
+function managerAuthDisabled() {
+  return process.env.MANAGER_MODE === "true";
+}
 
-export const { GET, POST } = handlers;
+export async function GET(request: Request) {
+  if (managerAuthDisabled()) return new Response(null, { status: 404 });
+  const { handlers } = await import("@/auth");
+  return handlers.GET(request);
+}
+
+export async function POST(request: Request) {
+  if (managerAuthDisabled()) return new Response(null, { status: 404 });
+  const { handlers } = await import("@/auth");
+  return handlers.POST(request);
+}