4c73439bd6
- Add backend API endpoint /api/users/system-strategies for system-wide strategy data - Query all strategies across all users with positions, PnL, trade stats - Add summary statistics (total strategies, running count, total capital, total PnL/ROI) - Support filtering by status (running/stopped) and search by strategy/symbol/user - Add System Overview tab with summary cards and detailed strategy table - Display user, strategy name, status, symbol, capital, PnL/ROI, positions, trades, indicator, exchange, timeframe, leverage - Add i18n translations for zh-CN and en-US - Lazy-load strategy data when tab is first accessed