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/lib/i18n/messages/en/reviews.json

@@ -34,5 +34,10 @@
   "reviews.titleAccent": "review",
   "reviews.approveAllConfirm": "Confirm ({count})",
   "reviews.action.approveShort": "OK",
-  "reviews.action.resetShort": "Re-review"
+  "reviews.action.resetShort": "Re-review",
+  "reviews.xliffHint": "XLIFF is the standard exchange format for translation reviews — export the segments, correct them in your own tool or send them to a reviewer, then import them back.",
+  "reviews.error.sessionExpired": "Your session has expired. Log in again and reload this page.",
+  "reviews.error.notFound": "This job no longer exists. It may have been cleaned up.",
+  "reviews.error.rateLimited": "Too many requests — wait a few seconds and retry.",
+  "reviews.error.server": "The server could not process this. Try again in a moment."
 }

frontend/src/lib/i18n/messages/en/translate.json

@@ -62,8 +62,8 @@
   "translate.chooseTargetLang": "Please choose a target language",
   "translate.pleaseLoadFile": "Please upload a file first",
   "translate.contextEngineActive": "Contextual engine active",
-  "translate.phase1": "Phase 1: Initialisation",
-  "translate.phase2": "Phase 2: Contextual reconstruction",
+  "translate.phase1": "Step 1: Analysing the document",
+  "translate.phase2": "Step 2: Translating & rebuilding layout",
   "translate.stat.time": "time",
   "translate.download": "Download",
   "translate.newTranslation": "+ New translation",
@@ -96,5 +96,10 @@
   "translate.downloadFailed": "The download failed. Please try again.",
   "translate.recent.title": "Recent translations",
   "translate.recent.review": "Review",
-  "translate.upload.ariaDropzone": "Upload a document: drag and drop, or press Enter to browse files"
+  "translate.upload.ariaDropzone": "Upload a document: drag and drop, or press Enter to browse files",
+  "translate.cancelAction": "Cancel translation",
+  "translate.cancelledTitle": "Translation cancelled",
+  "translate.cancelledDesc": "The job was stopped and the reserved document slot released.",
+  "translate.cancelFailedTitle": "Could not cancel",
+  "translate.cancelFailedDesc": "The job may have already finished. The display will update shortly."
 }

frontend/src/lib/i18n/messages/fr/reviews.json

@@ -34,5 +34,10 @@
   "reviews.titleAccent": "traduction",
   "reviews.approveAllConfirm": "Confirmer ({count})",
   "reviews.action.approveShort": "OK",
-  "reviews.action.resetShort": "À relire"
+  "reviews.action.resetShort": "À relire",
+  "reviews.xliffHint": "XLIFF est le format d'échange standard des relectures — exportez les segments, corrigez-les dans votre outil ou envoyez-les à un réviseur, puis réimportez-les.",
+  "reviews.error.sessionExpired": "Votre session a expiré. Reconnectez-vous puis rechargez cette page.",
+  "reviews.error.notFound": "Ce job n'existe plus. Il a peut-être été nettoyé.",
+  "reviews.error.rateLimited": "Trop de requêtes — attendez quelques secondes et réessayez.",
+  "reviews.error.server": "Le serveur n'a pas pu traiter la demande. Réessayez dans un instant."
 }

frontend/src/lib/i18n/messages/fr/translate.json

@@ -62,8 +62,8 @@
   "translate.chooseTargetLang": "Veuillez choisir une langue cible",
   "translate.pleaseLoadFile": "Veuillez charger un fichier d'abord",
   "translate.contextEngineActive": "Moteur contextuel actif",
-  "translate.phase1": "Phase 1 : Initialisation",
-  "translate.phase2": "Phase 2 : Reconstruction contextuelle",
+  "translate.phase1": "Étape 1 : Analyse du document",
+  "translate.phase2": "Étape 2 : Traduction et reconstruction de la mise en page",
   "translate.stat.time": "temps",
   "translate.download": "Télécharger",
   "translate.newTranslation": "+ Nouvelle traduction",
@@ -96,5 +96,10 @@
   "translate.downloadFailed": "Le téléchargement a échoué. Réessayez.",
   "translate.recent.title": "Traductions récentes",
   "translate.recent.review": "Relire",
-  "translate.upload.ariaDropzone": "Déposer un document : glisser-déposer ou appuyer sur Entrée pour parcourir"
+  "translate.upload.ariaDropzone": "Déposer un document : glisser-déposer ou appuyer sur Entrée pour parcourir",
+  "translate.cancelAction": "Annuler la traduction",
+  "translate.cancelledTitle": "Traduction annulée",
+  "translate.cancelledDesc": "Le job a été arrêté et le document réservé a été libéré.",
+  "translate.cancelFailedTitle": "Annulation impossible",
+  "translate.cancelFailedDesc": "Le job est peut-être déjà terminé. L'affichage se mettra à jour sous peu."
 }