fix: 修 POST /api/v1/conversations 的 MissingGreenlet（会话建不出来导致转人工 404）

- public_platform_service: 创建 ConversationSession 时显式赋值四个 server_default 时间列，
  否则 flush() 后需回读数据库生成值，在 async session 里以同步属性访问触发
  MissingGreenlet，接口 500，连带转人工一直报会话不存在
- portal: 客服改用 C001 真实建会话；转人工改传 reason_code/reason_detail（原 reason 属额外字段 422）
- portal: 投顾查客户投资目标走 customers/{id} 变体
- seed/grant: 补 investment-goal:{read,write,confirm}:customer 三个动态拼出的权限码
  （data_scope=own_customers，投顾只看名下客户）

tools/grant_advisor_role.py

@@ -80,6 +80,12 @@ ADVISOR_GRANTED_CODES: tuple[str, ...] = (
     "investment-goal:read:self",
     "investment-goal:write:self",      # 新建投资目标
     "investment-goal:confirm:self",    # 与客户确认目标
+    # 看/建/确认**客户**（而非自己）的投资目标。这三个码是 `investment_goal_service.py`
+    # 按 `customer_id == 自己` 动态拼出来的，`data_scope=own_customers`：
+    # 只有客户在投顾名下才放行 —— 投顾服务的本来就是别人的钱。
+    "investment-goal:read:customer",
+    "investment-goal:write:customer",
+    "investment-goal:confirm:customer",
     "investment-goal:review",
     "investment-goal:publish",
     "portfolio-analysis:read:self",