fix(04-07): remove debug code — public page restored

Root cause: INTERNAL_SECRET was on same line as HOST= in .env (no trailing
newline when appended), so proxy middleware got empty secret and rejected
all /api/internal/validate-* calls → rewrote every /client/* request to
/not-found without running the page component.

src/app/client/[token]/page.tsx

@@ -90,8 +90,6 @@ export default async function ClientPage({
   params: Promise<{ token: string }>;
 }) {
   const { token } = await params;
-  const { appendFileSync } = await import("fs");
-  appendFileSync("/tmp/clienthub-debug.log", `[${new Date().toISOString()}] PAGE token=${token}\n`);
 
   const clientData = await getCachedClientData(token);
   if (!clientData) notFound();