feat: add full-margin position sizing mode across four exchanges

Env POSITION_SIZING_MODE switches risk vs full-margin (available*buffer, BTC/ETH 10x). Blocks trend/roll/key auto opens in full margin, purges breakout/fib monitors with WeChat notice, keeps RR check and initial SL snapshot for records.

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

crypto_monitor_gate_bot/templates/index.html

@@ -302,7 +302,13 @@
                 按风险比例自动计算仓位
             </div>
             <div class="rule-tip">
-                以损定仓：风险 {{ risk_percent }}% ｜移动保本：下单可勾选关闭；开启时 {{ breakeven_rr_trigger }}R 触发（每 1R 阶梯上移），偏移 {{ breakeven_offset_pct }}%
+                计仓模式：<strong>{{ position_sizing_mode_label }}</strong>（仅 .env <code>POSITION_SIZING_MODE</code>，须无仓后重启）
+                {% if position_sizing_mode == 'full_margin' %}
+                ｜全仓：合约可用×{{ full_margin_buffer_ratio }}，BTC/ETH {{ btc_leverage }}x、其它 {{ alt_leverage }}x，单仓；张数按交易所精度
+                {% else %}
+                ｜以损定仓：风险 {{ risk_percent }}%
+                {% endif %}
+                ｜移动保本：下单可勾选关闭；开启时 {{ breakeven_rr_trigger }}R 触发（每 1R 阶梯上移），偏移 {{ breakeven_offset_pct }}%
             </div>
             <div class="rule-tip">
                 划转：自动划转 {{ '开启' if auto_transfer_enabled else '关闭' }}（每天<strong>北京时间 {{ auto_transfer_bj_hour }}:00</strong>起该整点小时内尝试；账簿按 <strong>UTC 自然日</strong>去重；界面时间为北京；将 {{ auto_transfer_to }} 补足到 {{ money_fmt(auto_transfer_amount) }}U，来自 {{ auto_transfer_from }}）
@@ -346,7 +352,7 @@
                 <input id="order-tp" name="tgt" step="any" placeholder="止盈价格" required>
                 <input id="order-sl-pct" name="sl_pct" type="number" min="0.01" step="0.01" placeholder="止损%" style="display:none">
                 <input id="order-tp-pct" name="tp_pct" type="number" min="0.01" step="0.01" placeholder="止盈%" style="display:none">
-                <button type="submit">开仓（以损定仓）</button>
+                <button type="submit">{{ open_position_button_label }}</button>
             </form>
             <div class="order-live-positions">
                 <h3 style="margin:0 0 2px;font-size:.95rem;color:#b8c4ff">实时持仓</h3>