feat(hub-ai): paste screenshots in chat and include position TP/SL in coach context

Let users paste images into AI chat with removable pending attachments, and feed exchange/monitor stop-loss and take-profit into trading coach snapshots so replies reflect actual protection on open positions.

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

manual_trading_hub/static/index.html

@@ -561,13 +561,13 @@
               <div id="ai-chat-messages" class="ai-panel-scroll ai-chat-messages" aria-live="polite"></div>
               <form id="ai-chat-form" class="ai-chat-form">
                 <div class="ai-chat-compose">
-                  <textarea id="ai-chat-input" rows="2" placeholder="聊聊行情、心态、纪律、执行…" autocomplete="off"></textarea>
+                  <textarea id="ai-chat-input" rows="2" placeholder="聊聊行情、心态、纪律、执行…；可直接 Ctrl+V 粘贴截图" autocomplete="off"></textarea>
+                  <div id="ai-chat-pending" class="ai-chat-pending-list" aria-live="polite"></div>
                   <div class="ai-chat-compose-actions">
                     <label class="ai-chat-upload-btn" title="上传图片或 txt/md/json 文档">
                       <input type="file" id="ai-chat-files" accept="image/*,.txt,.md,.markdown,.json" multiple hidden />
                       附件
                     </label>
-                    <span id="ai-chat-files-label" class="ai-chat-files-label"></span>
                     <button type="submit" id="btn-ai-chat-send" class="primary">发送</button>
                   </div>
                 </div>