feat(phase6): Add sounds, team chat, reactions, monitor, settings, and CSV import/export

Sound System:
- Add soundStore with volume/mute persistence
- Add useSound hook with Web Audio API fallback
- Add SoundControl component for in-game volume adjustment
- Play sounds for correct/incorrect, steal, timer, victory/defeat

Team Chat:
- Add TeamChat component with collapsible panel
- Add team_message WebSocket event (team-only visibility)
- Store up to 50 messages per session

Emoji Reactions:
- Add EmojiReactions bar with 8 emojis
- Add ReactionOverlay with floating animations (Framer Motion)
- Add rate limiting (1 reaction per 3 seconds)
- Broadcast reactions to all players in room

Admin Monitor:
- Add Monitor page showing active rooms from Redis
- Display player counts, team composition, status
- Add ability to close problematic rooms

Admin Settings:
- Add Settings page for game configuration
- Configure points/times by difficulty, steal penalty, max players
- Store config in JSON file with service helpers

CSV Import/Export:
- Add export endpoint with optional filters
- Add import endpoint with validation and error reporting
- Add UI buttons and import result modal in Questions page

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

frontend/src/stores/gameStore.ts

@@ -1,6 +1,23 @@
 import { create } from 'zustand'
 import type { GameRoom, Question, ChatMessage, Achievement } from '../types'
 
+export interface Reaction {
+  id: string
+  player_name: string
+  team: 'A' | 'B'
+  emoji: string
+  timestamp: string
+}
+
+export interface TeamMessage {
+  player_name: string
+  team: 'A' | 'B'
+  message: string
+  timestamp: string
+}
+
+const MAX_TEAM_MESSAGES = 50
+
 interface GameState {
   // Room state
   room: GameRoom | null
@@ -23,6 +40,11 @@ interface GameState {
   addMessage: (message: ChatMessage) => void
   clearMessages: () => void
 
+  // Team chat messages
+  teamMessages: TeamMessage[]
+  addTeamMessage: (message: TeamMessage) => void
+  clearTeamMessages: () => void
+
   // Achievements
   achievements: Achievement[]
   setAchievements: (achievements: Achievement[]) => void
@@ -44,6 +66,12 @@ interface GameState {
   showStealPrompt: boolean
   setShowStealPrompt: (show: boolean) => void
 
+  // Reactions
+  reactions: Reaction[]
+  addReaction: (reaction: Omit<Reaction, 'id'>) => void
+  removeReaction: (id: string) => void
+  clearReactions: () => void
+
   // Game result
   gameResult: {
     winner: 'A' | 'B' | null
@@ -88,6 +116,13 @@ export const useGameStore = create<GameState>((set) => ({
     set((state) => ({ messages: [...state.messages, message].slice(-100) })),
   clearMessages: () => set({ messages: [] }),
 
+  teamMessages: [],
+  addTeamMessage: (message) =>
+    set((state) => ({
+      teamMessages: [...state.teamMessages, message].slice(-MAX_TEAM_MESSAGES),
+    })),
+  clearTeamMessages: () => set({ teamMessages: [] }),
+
   achievements: [],
   setAchievements: (achievements) => set({ achievements }),
   unlockAchievement: (id) =>
@@ -105,6 +140,20 @@ export const useGameStore = create<GameState>((set) => ({
   showStealPrompt: false,
   setShowStealPrompt: (showStealPrompt) => set({ showStealPrompt }),
 
+  reactions: [],
+  addReaction: (reaction) =>
+    set((state) => ({
+      reactions: [
+        ...state.reactions,
+        { ...reaction, id: `${Date.now()}-${Math.random().toString(36).substr(2, 9)}` },
+      ],
+    })),
+  removeReaction: (id) =>
+    set((state) => ({
+      reactions: state.reactions.filter((r) => r.id !== id),
+    })),
+  clearReactions: () => set({ reactions: [] }),
+
   gameResult: null,
   setGameResult: (gameResult) => set({ gameResult }),
 
@@ -114,6 +163,8 @@ export const useGameStore = create<GameState>((set) => ({
       currentQuestion: null,
       timerEnd: null,
       messages: [],
+      teamMessages: [],
+      reactions: [],
       stats: initialStats,
       showStealPrompt: false,
       gameResult: null,