feat(frontend): 添加 Zustand store 架构

- 创建 5 个领域 store：runtimeStore, marketStore, portfolioStore, agentStore, uiStore
- 更新 CLAUDE.md 记录架构改进
- Zustand 已安装但 stores 尚未在 App.jsx 中使用（渐进迁移）

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

frontend/src/store/portfolioStore.js

@@ -0,0 +1,38 @@
+import { create } from 'zustand';
+
+/**
+ * Portfolio Store - Portfolio data, holdings, trades, statistics
+ */
+export const usePortfolioStore = create((set) => ({
+  // Portfolio data
+  portfolioData: {
+    netValue: 10000,
+    pnl: 0,
+    equity: [],
+    baseline: [],
+    baseline_vw: [],
+    momentum: [],
+    strategies: [],
+    equity_return: 0,
+    baseline_return: 0,
+    baseline_vw_return: 0,
+    momentum_return: 0,
+  },
+  setPortfolioData: (portfolioData) => set({ portfolioData }),
+
+  // Holdings
+  holdings: [],
+  setHoldings: (holdings) => set({ holdings }),
+
+  // Trades
+  trades: [],
+  setTrades: (trades) => set({ trades }),
+
+  // Statistics
+  stats: null,
+  setStats: (stats) => set({ stats }),
+
+  // Leaderboard
+  leaderboard: [],
+  setLeaderboard: (leaderboard) => set({ leaderboard }),
+}));