fix: 品种推荐改为最大手数并补算旧缓存。

- 最大手数 = floor(权益×保证金上限%÷1手保证金)
- 加载与 SSE 推送时实时补算，旧缓存缺字段时自动刷新

Co-authored-by: Cursor <cursoragent@cursor.com>

static/js/trade.js

@@ -639,7 +639,7 @@
                 '<td>' + (r.ref_take_profit != null ? r.ref_take_profit : '—') + '</td>' +
                 '<td>' + (r.margin_one_lot != null ? r.margin_one_lot : '—') + '</td>' +
                 '<td>' + (r.open_fee_one_lot != null ? r.open_fee_one_lot : '—') + '</td>' +
-                '<td>' + (r.recommended_lots != null && r.recommended_lots > 0 ? r.recommended_lots : '—') + '</td>' +
+                '<td>' + (r.max_lots != null && r.max_lots > 0 ? r.max_lots : '—') + '</td>' +
                 '<td><span class="badge ' + (r.status === 'ok' ? 'profit' : 'planned') + '">' + (r.status_label || '') + '</span></td>' +
                 '</tr>'
             );