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_okx/templates/index.html

@@ -426,7 +426,13 @@
                 人工开仓盈亏比不得低于 {{ manual_min_planned_rr }}:1
             </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 {{ auto_transfer_amount }}U，来自 {{ auto_transfer_from }}）
@@ -458,7 +464,9 @@
                     <option value="trend">趋势单</option>
                     <option value="swing">波段单</option>
                 </select>
+                {% if position_sizing_mode != 'full_margin' %}
                 <input id="order-leverage" name="leverage" type="number" min="1" step="1" placeholder="杠杆(可选)">
+                {% endif %}
                 <label style="display:flex;align-items:center;gap:4px;font-size:.82rem;color:#cfd3ef">
                     <input type="checkbox" name="breakeven_enabled" value="1" checked> 启用移动保本（关闭则仅保留初始止损与交易所挂单）
                 </label>
@@ -470,7 +478,7 @@
                 <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>
         <div class="card">