feat(web): trade detail modal with prices, fees, timestamps

- Click any trade row in history table to open detail modal
- Modal shows 6 sections: 概览, 时间, 价差, 手续费, 多仓, 空仓
- Entries and exits displayed with 6 decimal precision
- Fee entry/exit and total fee displayed
- Open/close timestamps with full date-time format
- Duration, scale count, total amount, exit reason
- Orders sub-table if available
- Escape key and overlay click to close

web/static/style.css

@@ -166,3 +166,74 @@ tr:hover td { background: rgba(88, 166, 255, 0.05); }
   header { flex-direction: column; gap: 8px; }
   .stats-row { justify-content: center; }
 }
+
+/* Trade Detail Modal */
+.modal-overlay {
+  position: fixed;
+  top: 0; left: 0; right: 0; bottom: 0;
+  background: rgba(0,0,0,0.7);
+  z-index: 1000;
+  display: flex;
+  align-items: flex-start;
+  justify-content: center;
+  padding: 40px 16px;
+  overflow-y: auto;
+}
+.modal-content {
+  background: var(--card);
+  border: 1px solid var(--border);
+  border-radius: 12px;
+  max-width: 700px;
+  width: 100%;
+  box-shadow: 0 8px 32px rgba(0,0,0,0.5);
+}
+.modal-header {
+  display: flex;
+  justify-content: space-between;
+  align-items: center;
+  padding: 16px 20px;
+  border-bottom: 1px solid var(--border);
+}
+.modal-header h2 { font-size: 16px; margin: 0; padding: 0; border: none; color: var(--text); }
+.modal-close {
+  background: none;
+  border: none;
+  color: var(--text-dim);
+  font-size: 20px;
+  cursor: pointer;
+  padding: 4px 8px;
+  border-radius: 4px;
+  line-height: 1;
+}
+.modal-close:hover { background: rgba(255,255,255,0.1); color: var(--text); }
+#trade-detail-body { padding: 0; }
+.detail-grid {
+  display: grid;
+  grid-template-columns: 1fr 1fr;
+  gap: 0;
+}
+.detail-section {
+  padding: 14px 20px;
+  border-bottom: 1px solid rgba(48,54,61,0.4);
+}
+.detail-section:last-child { border-bottom: none; }
+.detail-section-full { grid-column: 1 / -1; }
+.detail-section h3 {
+  font-size: 12px;
+  color: var(--text-dim);
+  font-weight: 600;
+  text-transform: uppercase;
+  letter-spacing: 0.5px;
+  margin-bottom: 8px;
+}
+.detail-row {
+  display: flex;
+  justify-content: space-between;
+  padding: 3px 0;
+  font-size: 13px;
+}
+.detail-row .label { color: var(--text-dim); }
+.detail-row .value { font-weight: 500; }
+.detail-orders { width: 100%; font-size: 12px; }
+.detail-orders th { background: var(--bg); font-size: 10px; }
+.detail-orders td { padding: 4px 6px; }