feat(ui-polish): sidebar icons + topbar + dashboard redesign

- Sidebar: lucide-react icons, lock on gated items, upgrade badge on "Mon plan", user footer with avatar initials + plan label, "EX|PRIA" logo header
- Topbar: sticky with backdrop-blur, breadcrumb via centralized route-titles.ts, search placeholder, keyboard shortcuts + notifications icons
- Dashboard: split into Free/Standard/Premium views (ARCHITECTURE.md §3 aligned)
- NclcHero: NCLC display + gauge 5→10 + SVG score ring
- StatCards: simulations remaining + NCLC estimé + dernier score with delta
- RecentSimulations: 3 latest with NCLC badge + chevron nav
- NextStepCard: static recommendation per plan
- PaywallBanner: full-width redesign + fixed dead Boréal tokens
- Removed orphan MobileHeader.tsx (0 consumers)

Typecheck: OK · Tests: 122/122 ✅

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

docs/ROADMAP.md

@@ -94,6 +94,13 @@
 - Renommage tokens sur ~45 composants + inversion dark:/light: shadcn
 - ADR 006 mis à jour
 
+## Sprint UI Polish — Sidebar + Topbar + Dashboard ✅
+
+- Sidebar : icônes lucide, cadenas gating, badge upgrade, user footer, logo "EX|PRIA"
+- Topbar : sticky backdrop-blur, breadcrumb centralisé, recherche placeholder
+- Dashboard : split Free/Standard/Premium, NclcHero + StatCards + RecentSimulations + NextStepCard + PaywallBanner refonte
+- MobileHeader supprimé (remplacé par Topbar)
+
 ## Sprint 4 — Simulations EO (audio)
 
 16. MediaRecorder + upload audio EO T1/T3