feat: 完善智能体图片聊天与会话恢复

- 增加私有图片上传、绑定、历史回显与生命周期清理

- 支持输入草稿恢复、图片交互和模型图片能力约束

- 修复旧脏会话幂等删除与前端会话恢复

easyflow-ui-admin/app/src/utils/agent-chat-cache.ts

@@ -0,0 +1,83 @@
+const COMPOSER_SHADOW_PREFIX = 'easyflow:agent-composer-shadow';
+const RUNTIME_STORAGE_PREFIX = 'easyflow:agent-chat-runtime';
+
+type AccountIdentity =
+  | null
+  | undefined
+  | {
+      id?: number | string;
+      tenantId?: number | string;
+    };
+
+const clearListeners = new Set<(identity: string) => void>();
+
+/**
+ * 生成聊天本地缓存使用的账号隔离标识。
+ */
+export function resolveAgentChatIdentity(account: AccountIdentity) {
+  if (!account?.id) {
+    return '';
+  }
+  return `${String(account.tenantId || 'default')}:${String(account.id)}`;
+}
+
+/**
+ * 注册账号聊天缓存清理监听器。
+ */
+export function onAgentChatCacheClear(listener: (identity: string) => void) {
+  clearListeners.add(listener);
+  return () => clearListeners.delete(listener);
+}
+
+/**
+ * 清理指定账号的草稿影子和运行快照。
+ */
+export function clearAgentChatBrowserCache(account: AccountIdentity) {
+  const identity = resolveAgentChatIdentity(account);
+  if (!identity) {
+    return;
+  }
+  removeStorageEntries(safeStorage('localStorage'), [
+    `${COMPOSER_SHADOW_PREFIX}:${identity}:`,
+  ]);
+  removeStorageEntries(safeStorage('sessionStorage'), [
+    `${RUNTIME_STORAGE_PREFIX}:${identity}:`,
+  ]);
+  for (const listener of clearListeners) {
+    listener(identity);
+  }
+}
+
+/** 草稿影子存储前缀。 */
+export { COMPOSER_SHADOW_PREFIX, RUNTIME_STORAGE_PREFIX };
+
+function removeStorageEntries(
+  storage: Storage | undefined,
+  prefixes: string[],
+) {
+  if (!storage) {
+    return;
+  }
+  try {
+    const keys: string[] = [];
+    for (let index = 0; index < storage.length; index++) {
+      const key = storage.key(index);
+      if (key && prefixes.some((prefix) => key.startsWith(prefix))) {
+        keys.push(key);
+      }
+    }
+    for (const key of keys) {
+      storage.removeItem(key);
+    }
+  } catch {
+    // 浏览器禁用存储时，登录退出流程仍应继续。
+  }
+}
+
+function safeStorage(type: 'localStorage' | 'sessionStorage') {
+  try {
+    return globalThis[type];
+  } catch {
+    return undefined;
+  }
+}