feat: user menu + profile page + in-app subscription management

User-facing identity:
- UserMenu component in dashboard header: avatar (deterministic colour from
  email hash), email + name, current plan badge, dropdown to Profile /
  Billing / Support / Your data / (Admin panel if isAdmin) / Sign out
- /settings/profile: editable display name; email + phone shown read-only
  (changing them requires support ticket — magic-link flow assumed)
- GET + PATCH /v1/account/profile

In-app subscription management (no more Stripe Portal redirect for the
common flows — cancellation, plan switch, invoice viewing all in-app):
- Billing status now combines DB state with a live Stripe lookup of the
  subscription details + last 5 invoices. Single roundtrip.
- POST /v1/billing/cancel       → schedules cancel_at_period_end
- POST /v1/billing/reactivate   → undo scheduled cancel
- POST /v1/billing/change-plan  → prorated swap between any tier+cycle
- /settings/billing rewritten: current plan card with renew/cancel date,
  big cancel button + reactivate flow, plan-switcher grid, invoice list with
  PDF + hosted-invoice links
- Stripe portal still linked at the bottom as the escape hatch for rare
  actions (payment-method update, address change). New-subscription Checkout
  still uses Stripe-hosted Checkout (industry standard for PCI).

Stripe SDK v22 / API 2024-09 fix: current_period_end moved to subscription
items; updated read paths accordingly.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/app/(dashboard)/layout.tsx

@@ -1,6 +1,7 @@
 import { CookieBanner } from '@/components/cookie-banner';
 import { Logo } from '@/components/logo';
 import { MobileActionBar } from '@/components/mobile-action-bar';
+import { UserMenu } from '@/components/user-menu';
 import { FileClock, LayoutGrid, Package, Server, Settings } from 'lucide-react';
 import Link from 'next/link';
 
@@ -29,12 +30,15 @@ export default function DashboardLayout({ children }: { children: React.ReactNod
               </NavLink>
             </nav>
           </div>
-          <Link
-            href="/servers/new"
-            className="hidden h-7 items-center gap-1.5 rounded-md bg-[--color-accent] px-2.5 text-[12px] font-medium text-white transition-colors duration-200 hover:bg-[#5557e8] sm:inline-flex"
-          >
-            + New server
-          </Link>
+          <div className="flex items-center gap-1 sm:gap-2">
+            <Link
+              href="/servers/new"
+              className="hidden h-7 items-center gap-1.5 rounded-md bg-[--color-accent] px-2.5 text-[12px] font-medium text-white transition-colors duration-200 hover:bg-[#5557e8] sm:inline-flex"
+            >
+              + New server
+            </Link>
+            <UserMenu />
+          </div>
         </div>
       </header>
       <main className="flex-1 bg-[--color-bg] pb-20 sm:pb-0">{children}</main>