feat(frontend): 完成 Zustand 状态管理迁移

- 将 App.jsx 中的 useState 迁移到 5 个 Zustand stores
- useRuntimeStore: 连接状态、运行时配置
- useMarketStore: 市场数据、股票价格
- usePortfolioStore: 组合、持仓、交易
- useAgentStore: Agent 技能，工作区
- useUIStore: UI 状态、视图切换
- 保留 tickers useState（需与 INITIAL_TICKERS 同步）
- 恢复 newsApi.js 和 tradingApi.js

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

frontend/src/services/tradingApi.js

@@ -0,0 +1,55 @@
+const trimTrailingSlash = (value) => value.replace(/\/+$/, '');
+const isLocalDevHost = () => {
+  if (typeof window === 'undefined') {
+    return false;
+  }
+  const host = String(window.location.hostname || '').trim().toLowerCase();
+  return host === 'localhost' || host === '127.0.0.1';
+};
+
+const TRADING_SERVICE_BASE = trimTrailingSlash(import.meta.env.VITE_TRADING_SERVICE_URL || '') || (
+  isLocalDevHost() ? 'http://localhost:8001' : ''
+);
+
+export function hasDirectTradingService() {
+  return Boolean(TRADING_SERVICE_BASE);
+}
+
+export async function fetchInsiderTradesDirect(ticker, startDate = null, endDate = null, limit = 50) {
+  if (!TRADING_SERVICE_BASE) {
+    throw new Error('Direct trading service is not configured');
+  }
+
+  const params = new URLSearchParams();
+  params.set('ticker', ticker);
+  params.set('limit', String(limit));
+  if (startDate) {
+    params.set('start_date', startDate);
+  }
+  if (endDate) {
+    params.set('end_date', endDate);
+  }
+
+  const response = await fetch(`${TRADING_SERVICE_BASE}/api/insider-trades?${params.toString()}`);
+  if (!response.ok) {
+    throw new Error(await response.text());
+  }
+  return response.json();
+}
+
+export async function fetchStockHistoryDirect(ticker, startDate, endDate) {
+  if (!TRADING_SERVICE_BASE) {
+    throw new Error('Direct trading service is not configured');
+  }
+
+  const params = new URLSearchParams();
+  params.set('ticker', ticker);
+  params.set('start_date', startDate);
+  params.set('end_date', endDate);
+
+  const response = await fetch(`${TRADING_SERVICE_BASE}/api/prices?${params.toString()}`);
+  if (!response.ok) {
+    throw new Error(await response.text());
+  }
+  return response.json();
+}