fix(trend): surface DCA block reasons and ensure gate_bot poll thread

Log poll exceptions, diagnose live-trading and mark-price blocks on the trend page, start background monitors on app import, and add /api/trend_poll_status for debugging.

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

strategy_templates/strategy_trend_panel.html

@@ -7,6 +7,19 @@
         ② <strong>确认执行</strong>：市价首仓 50% + 挂交易所止损；首仓后可<strong>手动保本</strong>（默认均价+{{ trend_manual_breakeven_offset_pct }}%）；剩余 50% 在止损与补仓区间之间共 {{ trend_pullback_dca_legs }} 档（做多为<strong>上沿</strong>、做空为<strong>下沿</strong>；程序可能因最小张数自动减档）市价补仓；<strong>止盈由程序监控</strong>。<br>
         确认执行时若当前可用余额与预览快照相对偏差 &gt; <strong>{{ trend_preview_max_drift_pct }}%</strong> 会拒绝并要求重新预览。
     </div>
+    {% if trend_dca_probes %}
+    {% for p in trend_dca_probes %}
+    {% if p.trigger_reached and p.block_reason %}
+    <div class="rule-tip" style="margin-bottom:10px;border-color:#a55;background:#2a1818;color:#ffb4b4">
+        <strong>计划 #{{ p.plan_id }}</strong> 标记价 {{ p.mark_price }} 已触达补仓触发价 {{ p.next_trigger }}，但未自动补仓：
+        {{ p.block_reason }}。
+        {% if not live_trading_enabled %}
+        请在 <code>crypto_monitor_gate_bot/.env</code> 设置 <code>LIVE_TRADING_ENABLED=true</code> 后重启 PM2 进程 <strong>crypto_gate_bot</strong>（不是 manual-agent-gate-bot）。
+        {% endif %}
+    </div>
+    {% endif %}
+    {% endfor %}
+    {% endif %}
     <form id="trend-pullback-form" action="{{ url_for('preview_trend_pullback') }}" method="post" class="form-row">
         <input name="symbol" placeholder="BTC 或 ETH/USDT" required>
         <select name="direction" id="trend-direction" required>