refactor: 프론트엔드 TypeScript 타입 안전성 및 커스텀 훅 분리

- types/trading.ts: 중앙 타입 정의 (CandleData, Position, Trade 등)
- useMarketData.ts: 실시간 시세 처리 + 500ms 쓰로틀링
- usePortfolioData.ts: React Query 기반 포트폴리오 데이터 훅
- useTradeActions.ts: 매매 실행 액션 훅
- useWebSocket.ts: pong timeout 10초 감지 (좀비 연결 방지)
- TradingChart.tsx: @ts-nocheck 제거, CandleData 타입 적용
- PortfolioPanel/RecommendationPanel: any → 구체적 타입 교체
- Dashboard.tsx: 상태 관리 로직을 커스텀 훅으로 이전

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/hooks/useTradeActions.ts

@@ -0,0 +1,68 @@
+import { useCallback } from 'react'
+import { useQueryClient } from '@tanstack/react-query'
+import api from '../lib/api'
+
+export const useTradeActions = () => {
+    const queryClient = useQueryClient()
+
+    const handleSell = useCallback(
+        async (
+            stockCode: string,
+            stockName: string,
+            quantity: number
+        ): Promise<void> => {
+            try {
+                await api.post('/portfolio/sell', {
+                    stock_code: stockCode,
+                    quantity,
+                    price: null,
+                })
+
+                // Invalidate queries to refresh portfolio
+                queryClient.invalidateQueries({
+                    queryKey: ['portfolio-combined'],
+                })
+                queryClient.invalidateQueries({
+                    queryKey: ['trade-history'],
+                })
+
+                console.log(`✅ ${stockName} sell order completed`)
+            } catch (error: any) {
+                console.error(
+                    `❌ Sell order failed for ${stockName}:`,
+                    error.response?.data?.detail || error.message
+                )
+                throw error
+            }
+        },
+        [queryClient]
+    )
+
+    const resetPendingTrades = useCallback(async (): Promise<void> => {
+        try {
+            const response = await api.delete('/trades/pending')
+            queryClient.invalidateQueries({
+                queryKey: ['trade-history'],
+            })
+            console.log('✅ Pending orders cleared:', response.data)
+        } catch (error: any) {
+            console.error(
+                '❌ Failed to clear pending orders:',
+                error.response?.data?.detail || error.message
+            )
+            throw error
+        }
+    }, [queryClient])
+
+    const invalidateTradeHistory = useCallback(() => {
+        queryClient.invalidateQueries({
+            queryKey: ['trade-history'],
+        })
+    }, [queryClient])
+
+    return {
+        handleSell,
+        resetPendingTrades,
+        invalidateTradeHistory,
+    }
+}