feat(mvp): phase 7 - UI polish & ambient backgrounds

Add layout system (sidebar, header, main layout), dark/light/system theme
with HSL customization, 3 ambient backgrounds (mesh gradient, particle field,
aurora), Cmd/Ctrl+K search dialog, page transitions, card hover effects,
status pulse animations, skeleton loaders, and responsive design. Polish
all existing pages with consistent theming.

plans/mvp-web-app-launcher/PLAN.md

@@ -33,7 +33,7 @@ Build a self-hosted web application launcher/dashboard for a TrueNAS server envi
 - [x] Phase 4: App Registry & Healthcheck [fullstack] → [subplan](./phase-4-app-healthcheck.md)
 - [ ] Phase 5: Board, Section & Widget System [fullstack] → [subplan](./phase-5-board-widgets.md)
 - [x] Phase 6: Admin Panel [fullstack] → [subplan](./phase-6-admin-panel.md)
-- [ ] Phase 7: UI Polish & Ambient Backgrounds [frontend] → [subplan](./phase-7-ui-polish.md)
+- [x] Phase 7: UI Polish & Ambient Backgrounds [frontend] → [subplan](./phase-7-ui-polish.md)
 - [ ] Phase 8: Integration, Testing & Deployment [fullstack] → [subplan](./phase-8-integration-deploy.md)
 
 ## Phase Progress Log
@@ -46,7 +46,7 @@ Build a self-hosted web application launcher/dashboard for a TrueNAS server envi
 | Phase 4: App & Healthcheck | fullstack | ✅ Complete | ⬜ | ⬜ | ⬜ |
 | Phase 5: Board & Widgets | fullstack | ✅ Complete | ⬜ | ⬜ | ⬜ |
 | Phase 6: Admin Panel | fullstack | ✅ Complete | ⬜ | ⬜ | ⬜ |
-| Phase 7: UI Polish | frontend | ⬜ Not Started | ⬜ | ⬜ | ⬜ |
+| Phase 7: UI Polish | frontend | ✅ Complete | ⬜ | ⬜ | ⬜ |
 | Phase 8: Integration & Deploy | fullstack | ⬜ Not Started | ⬜ | ⬜ | ⬜ |
 
 ## Final Review