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/stores/gameStore.ts

@@ -1,5 +1,5 @@
 import { create } from 'zustand'
-import type { GameRoom, Player, Question, ChatMessage, Achievement } from '../types'
+import type { GameRoom, Question, ChatMessage, Achievement } from '../types'
 
 interface GameState {
   // Room state
@@ -44,6 +44,19 @@ interface GameState {
   showStealPrompt: boolean
   setShowStealPrompt: (show: boolean) => void
 
+  // Game result
+  gameResult: {
+    winner: 'A' | 'B' | null
+    finalScores: { A: number; B: number }
+    replayCode: string | null
+    achievementsUnlocked: Array<{
+      player_name: string
+      team: 'A' | 'B'
+      achievement: Achievement
+    }>
+  } | null
+  setGameResult: (result: GameState['gameResult']) => void
+
   // Reset
   resetGame: () => void
 }
@@ -92,6 +105,9 @@ export const useGameStore = create<GameState>((set) => ({
   showStealPrompt: false,
   setShowStealPrompt: (showStealPrompt) => set({ showStealPrompt }),
 
+  gameResult: null,
+  setGameResult: (gameResult) => set({ gameResult }),
+
   resetGame: () =>
     set({
       room: null,
@@ -100,5 +116,6 @@ export const useGameStore = create<GameState>((set) => ({
       messages: [],
       stats: initialStats,
       showStealPrompt: false,
+      gameResult: null,
     }),
 }))