Add e2e/ux.spec.ts covering the ⌘K search palette, lesson detail page,
stats sections, and the legacy /admin → /lessons redirect.
Also fixes two issues uncovered by running the full suite:
- Skip auth rate limiter in e2e by running the backend with NODE_ENV=test
(registration limit of 5 was tripping later tests).
- Render the card table for lesson owners even when the lesson has zero
cards, so the first card can be added from the detail page.
Applied ui-ux-pro-max design system recommendations:
- Tailwind theme: study purple primary + correct green accent
- Inter + Plus Jakarta Sans typography
- Glassmorphic surfaces with soft shadows and mesh background
- Real 3D card flip with spring physics + answer feedback flash
- Gradient stat cards, progress bar, animated done screen with score ring
- Polished Layout, Dashboard, Admin, AdminLesson, CardTable, ImportDialog, PracticeSetup, Practice, PracticeDone
- E2E smoke updated for new accessible names
