docs: add Phase 8 — Mobile Layout + PWA

.planning/REQUIREMENTS.md

@@ -81,6 +81,15 @@ Requirements for beta-ready release. Each maps to roadmap phases.
 - [x] **I18N-05**: Error messages, validation text, and system notifications are localized
 - [x] **I18N-06**: Adding a new language requires only translation files, not code changes (extensible i18n architecture)
 
+### Mobile + PWA
+
+- [ ] **MOB-01**: All portal pages render correctly and are usable on mobile (320px–480px) and tablet (768px–1024px) screens
+- [ ] **MOB-02**: Sidebar collapses to a hamburger menu on mobile with smooth open/close animation
+- [ ] **MOB-03**: Chat interface is fully functional on mobile — send messages, see streaming responses, scroll history
+- [ ] **MOB-04**: Portal installable as a PWA with app icon, splash screen, and service worker for offline shell caching
+- [ ] **MOB-05**: Push notifications for new messages when PWA is installed (or service worker caches app shell for instant load)
+- [ ] **MOB-06**: All touch interactions feel native — no hover-dependent UI that breaks on touch devices
+
 ## v2 Requirements
 
 Deferred to future release. Tracked but not in current roadmap.
@@ -177,12 +186,20 @@ Which phases cover which requirements. Updated during roadmap creation.
 | I18N-05 | Phase 7 | Complete |
 | I18N-06 | Phase 7 | Complete |
 
+| MOB-01 | Phase 8 | Pending |
+| MOB-02 | Phase 8 | Pending |
+| MOB-03 | Phase 8 | Pending |
+| MOB-04 | Phase 8 | Pending |
+| MOB-05 | Phase 8 | Pending |
+| MOB-06 | Phase 8 | Pending |
+
 **Coverage:**
 - v1 requirements: 25 total (all complete)
 - RBAC requirements: 6 total (Phase 4, all complete)
 - Employee Design requirements: 5 total (Phase 5, all complete)
 - Web Chat requirements: 5 total (Phase 6, all complete)
-- Multilanguage requirements: 6 total (Phase 7)
+- Multilanguage requirements: 6 total (Phase 7, all complete)
+- Mobile + PWA requirements: 6 total (Phase 8)
 
 ---
 *Requirements defined: 2026-03-23*