Fix Gate/Binance memory regression and roll stop offset from avg.

Stop fetch_tickers fallback for volume rank and keep stale cache on failed refresh. Compute roll unified stop as merge-average plus offset percent instead of break-even.

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

strategy_templates/strategy_roll.html

@@ -48,7 +48,7 @@
         <h2 style="margin:0 0 8px">规则说明</h2>
         <div class="rule-tip">
             <strong>仅人工加仓</strong>，程序不会自动触发。须先在「实盘下单」有同向持仓。<br>
-            做多最多滚仓 <strong>3</strong> 次；止盈<strong>锁定首仓</strong>不变；每次填写<strong>新统一止损</strong>，总风险%按「合并持仓打到新止损≈账户风险」反推张数。<br>
+            做多最多滚仓 <strong>3</strong> 次；止盈<strong>锁定首仓</strong>不变；每次填写<strong>止损偏移%</strong>（相对合并均价，默认 1%），总风险%按「合并持仓打到新止损≈账户风险」反推张数。<br>
             斐波限价：上沿 H、下沿 L 仅用于算 0.618/0.786 加仓价（多：下沿=止损侧；空：上沿=止损侧）。<br>
             {% if trend_active %}<span style="color:#ff8f8f">当前有运行中的趋势回调计划，请先结束后再滚仓。</span>{% endif %}
         </div>
@@ -70,7 +70,7 @@
             </select>
             <input name="fib_upper" step="any" placeholder="上沿 H">
             <input name="fib_lower" step="any" placeholder="下沿 L">
-            <input name="new_stop_loss" step="any" placeholder="新统一止损" required>
+            <input name="stop_offset_pct" type="number" min="0.01" step="0.01" value="1" placeholder="止损偏移%(合并均价)" required>
             <input name="risk_percent" type="number" min="0.1" step="0.1" value="{{ default_risk_percent }}" placeholder="总风险%">
             <button type="submit" {% if trend_active %}disabled{% endif %} onclick="return confirm('确认按预览逻辑实盘加仓并更新止损？')">执行滚仓</button>
         </form>