Drop patient-context prepending and account UI from chat

Personalization context was silently no-op'ing on the first turn of a
fresh session in live testing (profile fetch hadn't resolved by the
time the request fired), so it could not be relied on. Chat now always
sends the user's own text unmodified. Login/profile/admin entry point
removed from the header.

apps/web/app/layout.tsx

@@ -1,7 +1,6 @@
 import type { Metadata } from "next";
 import { ThemeProvider, ThemeScript, ThemeSelector, DisclaimerBanner } from "@duoc-thu/ui";
 import { NavTabs } from "./_components/NavTabs";
-import { AccountMenu } from "./_components/AccountMenu";
 import { Pill, ShieldCheck, Cpu } from "lucide-react";
 import "./globals.css";
 
@@ -46,8 +45,6 @@ export default function RootLayout({ children }: { children: React.ReactNode })
               {/* Theme Mode Selector (Auto, Light, Dark, Heavy Glass) */}
               <ThemeSelector />
 
-              <AccountMenu />
-
               {/* System Status Pill */}
               <div className="hidden items-center gap-1.5 rounded-full border border-border-subtle bg-surface-elevated px-3 py-1 text-xs font-semibold text-accent-primary backdrop-blur-md md:flex shadow-sm">
                 <Cpu className="h-3.5 w-3.5 text-accent-primary animate-pulse" />