feat: 登录设备管理与编辑器图片上传

- 新增登录设备列表与会话下线（ListLoginDevices/RevokeLoginDevice），按设备指纹识别当前会话
- Markdown 编辑器新增图片插入弹窗与图片上传（ImageInsertModal）
- 实时总线、账号守卫与用户事件适配

frontend/app/globals.css

@@ -2088,6 +2088,100 @@ html.dark .j13-board-trigger.is-invalid .j13-board-trigger-hint {
   background: var(--panel-2) !important;
   color: var(--ink) !important;
 }
+/* 链接弹窗：高级选项折叠开关 + 站内帖子搜索区与结果行（标题 sans 字体 + 右侧标签） */
+.j13-md-adv-toggle {
+  display: inline-flex;
+  align-items: center;
+  gap: 4px;
+  align-self: flex-start;
+  padding: 2px 0;
+  border: 0;
+  appearance: none;
+  -webkit-appearance: none;
+  background: transparent !important;
+  color: var(--ink-3);
+  font-size: 12px;
+  font-weight: 600;
+  cursor: pointer;
+}
+.j13-md-adv-toggle:hover {
+  color: var(--ink);
+}
+.j13-md-link-search {
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+  margin-top: 2px;
+  padding-top: 8px;
+  border-top: 1px solid var(--line);
+}
+.j13-md-popover-list button.j13-md-post-row {
+  display: flex;
+  align-items: center;
+  gap: 8px;
+  font-family: inherit;
+  font-size: 12.5px;
+  font-weight: 500;
+}
+.j13-md-post-tag {
+  flex-shrink: 0;
+  font-size: 11px;
+  font-weight: 500;
+  color: var(--ink-3);
+}
+/* 插图统一弹窗：tab 行、拖拽上传区、错误行 */
+.j13-md-mode.j13-img-tabs {
+  display: flex;
+  width: 100%;
+}
+.j13-img-tabs button {
+  flex: 1;
+  justify-content: center;
+}
+.j13-img-tabs button:disabled {
+  opacity: 0.5;
+  cursor: not-allowed;
+}
+.j13-img-dropzone {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  justify-content: center;
+  gap: 8px;
+  width: 100%;
+  padding: 36px 16px;
+  border-radius: 14px;
+  border: 1.5px dashed var(--control-border);
+  background: var(--panel-2);
+  color: var(--ink-3);
+  cursor: pointer;
+  appearance: none;
+  -webkit-appearance: none;
+  transition: border-color 0.15s, background 0.15s;
+}
+.j13-img-dropzone:hover,
+.j13-img-dropzone.is-dragover {
+  border-color: var(--accent);
+  color: var(--ink-2);
+}
+.j13-img-dropzone:disabled {
+  opacity: 0.6;
+  cursor: progress;
+}
+.j13-img-dropzone-title {
+  font-size: 13.5px;
+  font-weight: 600;
+  color: var(--ink);
+}
+.j13-img-dropzone-hint {
+  font-size: 12px;
+  color: var(--ink-3);
+}
+.j13-img-modal-error {
+  margin-top: 10px;
+  font-size: 12.5px;
+  color: var(--danger, #b42318);
+}
 .j13-md-field {
   display: flex;
   flex-direction: column;