feat: gamified redesign — player card, daily quest, streaks and celeb…

[Faustze]

…rations

Implement the high-fidelity gamified redesign from the design handoff (design_handoff_gamified_redesign/README.md) on top of the existing Vue 3 + SCSS architecture:

• Design tokens: accent derivatives via color-mix, gold/green, denser cards, page background gradient, dark-theme overrides (_base.scss); calm keyframes only — floaty, fadeUp, popIn, riseFade, timerFill, confettiFly, ringPop (_animations.scss)
• UiButton: tactile / tactile-secondary variants with 3D press effect
• Sidebar: PlayerCard with SVG progress ring, XP bar and "+N XP" float; per-module +XP / done chips, locked categories block
• Dashboard: hero with floating code glyphs, DailyQuestBanner with midnight countdown and x2 reward, count-up stats (rAF with timeout fallback), level + week-streak card, categories grid
• Progress store: streak, daily quest, totalEarned with localStorage migration; completeModule returns a CompletionResult for celebrations
• Topic page: chips (category, difficulty, +XP, quest x2), dark code block, live debounce demo (silence-window timer bar + event stream)
• Celebrations behind feature flags: ConfettiBurst, LevelUpModal, useCelebration composable (config/features.ts)
• i18n: new EN/RU keys; fix modules.deepEqual key casing that broke translations on the deepEqual page
• Drop Nuxt pageTransition: it clashed with Suspense on async pages (insertBefore NotFoundError); screens animate via fadeUp on mount
• Tests: Vitest suite for streak/quest/XP logic; e2e specs updated for the new markup, fixture pins the daily quest for determinism