feat(phase4): Complete frontend with themes, replay, and results

Visual Effects:
- Add effects.css with neon glow, CRT scanlines, glitch, sparkles, RGB shift
- Animations work with all 5 themes (DRRR, Retro, Minimal, RGB, Anime)

Game Finished Handler:
- Add gameResult state to gameStore (winner, scores, replay, achievements)
- Handle game_finished WebSocket event in useSocket
- Store achievements unlocked by all players

Results Page:
- Show winner with animation (or tie)
- Display final scores with staggered animation
- List achievements unlocked per player
- Buttons for replay and new game

Replay Player:
- Fetch replay from API by code
- Auto-playback with configurable speed (1x, 2x, 4x)
- Play/Pause and timeline controls
- Events sidebar for navigation
- Animated event transitions

Lobby Updates:
- Load categories from API on mount
- Display available categories with icons
- Backend generates board (no hardcoded data)

TypeScript Fixes:
- Add vite-env.d.ts for import.meta.env types
- Fix ringColor style issues
- Remove unused imports

Build verified: npm run build succeeds

Phase 4 tasks completed:
- F4.1: CSS effects for themes
- F4.2: Results page with achievements
- F4.3: Replay player
- F4.4: game_finished handler
- F4.5: Lobby API integration
- F4.6: Build verification and fixes

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/App.tsx

@@ -13,7 +13,7 @@ function App() {
         <Route path="/lobby/:roomCode" element={<Lobby />} />
         <Route path="/game/:roomCode" element={<Game />} />
         <Route path="/results/:roomCode" element={<Results />} />
-        <Route path="/replay/:sessionId" element={<Replay />} />
+        <Route path="/replay/:replayCode" element={<Replay />} />
       </Routes>
     </div>
   )