feat(ui,api): wave 3 — editorial pricing, real cancel, server history, DeepL purge

Pricing: full editorial redesign — serif card headers with accent pills
replace the colored font-black blocks, tone sweep across toggle/metrics/
features/CTAs, PLAN_COLORS removed; one design system app-wide.

Translate: decorative titles one step down (CTA hierarchy restored);
glossary and image-translation blocks hidden entirely for free users
(progressive disclosure — three controls for free).

Reviews: XLIFF hint line explains the exchange format; backend errors
routed through a friendly mapper (session/not-found/rate-limit/server).

Landing: fabricated hero UI cards (fake 'Context Engine' overlay)
removed — the photo no longer promises screens that don't exist.

Nav: single DashboardNavLinks component shared by sidebar and mobile
drawer (was duplicated markup).

API: GET /api/v1/translations (user job history, paginated; completed
jobs retained 24h) and POST /api/v1/translations/{id}/cancel —
cooperative cancellation with worker checkpoints before dispatch and
before finalisation, reserved quota released immediately. Translate
monitor now offers a real 'Cancel translation' next to 'Back to start';
recent-jobs list reads server history first, localStorage fallback.

DeepL purge (backend): provider module, registry registration, config
attrs/defaults, dispatch branch, admin settings schema + test branch,
legacy availability block, validation rules, plan provider lists,
error-code mappings, MCP enums, translator prompt mention, related
tests updated/removed. Fallback resolver skips unknown providers, so
stale chains containing 'deepl' degrade gracefully.

Verified: backend 110 tests passed; frontend build exit 0, vitest 9/9,
0 missing i18n keys, eslint 63 errors (vs 64 at HEAD).

frontend/src/app/dashboard/DashboardHeader.tsx

@@ -2,30 +2,24 @@
 
 import { useState } from 'react';
 import Link from 'next/link';
-import { usePathname } from 'next/navigation';
 import {
   Menu,
   X,
   LogOut
 } from 'lucide-react';
-import { cn } from '@/lib/utils';
 import { useUser } from './useUser';
 import { useLogout } from './useLogout';
-import { baseNavItems } from './constants';
+import { DashboardNavLinks } from './DashboardNavLinks';
 import { getInitials, translateTier } from './utils';
 import { ThemeToggle } from '@/components/ui/theme-toggle';
 import { useI18n } from '@/lib/i18n';
 
 export function DashboardHeader() {
   const [mobileOpen, setMobileOpen] = useState(false);
-  const pathname = usePathname();
   const { data: user, isLoading } = useUser();
   const { logout } = useLogout();
   const { t } = useI18n();
 
-  const isPro = ['pro', 'business', 'enterprise'].includes(user?.tier ?? '');
-  const navItems = isPro ? baseNavItems : baseNavItems.filter(item => !item.proOnly);
-
   return (
     <>
       <header className="flex h-20 shrink-0 items-center justify-between border-b border-black/5 dark:border-white/5 bg-white/50 dark:bg-[#141414]/50 backdrop-blur-md px-6 lg:px-8">
@@ -97,25 +91,7 @@ export function DashboardHeader() {
       {mobileOpen && (
         <div className="border-b border-black/5 dark:border-white/5 bg-white dark:bg-[#141414] px-6 py-4 lg:hidden">
           <nav className="flex flex-col gap-1">
-            {navItems.map((item) => {
-              const isActive = pathname === item.href;
-              return (
-                <Link
-                  key={item.href}
-                  href={item.href}
-                  onClick={() => setMobileOpen(false)}
-                  className={cn(
-                    'flex items-center gap-4 rounded-2xl px-6 py-4 text-[11px] font-black uppercase tracking-[0.2em] transition-all duration-200',
-                    isActive
-                      ? 'bg-brand-dark text-white shadow-xl'
-                      : 'text-brand-dark/65 dark:text-white/65 hover:bg-brand-muted dark:hover:bg-[#1f1f1f]'
-                  )}
-                >
-                  <item.icon size={18} className="shrink-0" />
-                  {t(item.labelKey)}
-                </Link>
-              );
-            })}
+            <DashboardNavLinks onNavigate={() => setMobileOpen(false)} />
 
             <div className="my-3 h-px bg-black/5 dark:bg-white/5" />