refactor(auth): 去多身份/多端口——账号单一角色，删 user_identities/select-identity/多端口路由

- 删 UserIdentity 模型/IdentityRepository/db.identities，账号统一单一角色(users.role)
- auth.py 去 select-identity/_identity_summaries，登录恒返回 identities=[]；_login_response_for_user 按单角色签发
- 删多端口路由 rbac_government/investor/developer 及其 main 挂载
- seed 去多身份回填(_migrate_identities/_ensure_port_agents/多端身份/端口标签映射)
- dependencies: require_port 去端口隔离(单角色放宽)、optional_current_user 修 identity_id 多余参数
- user_admin_service create_user 不再建端口身份；schemas 去 SelectIdentityRequest
- 新增迁移 0014_drop_user_identities(drop user_identities 表)
- 测试改写为单角色契约(登录空 identities、无 select-identity、账号级智能体)

Co-Authored-By: Claude <noreply@anthropic.com>

app/services/user_admin_service.py

@@ -6,14 +6,6 @@ from fastapi import HTTPException
 
 from ..infrastructure.repositories import Database
 
-# 业务角色 → 端口映射（与领域规则一致）
-_PORT_FOR_ROLE = {
-    "opc_member": "opc", "carrier": "carrier", "enterprise": "enterprise",
-    "provider": "provider", "government": "government", "operator": "operator",
-    "investor": "investor", "developer": "developer",
-}
-
-
 class UserAdminService:
     """运营端账号/角色管理。"""
 
@@ -43,11 +35,6 @@ class UserAdminService:
             role=req.role, sub_role=req.sub_role, org_id=req.org_id, region_id=req.region_id,
             source="admin", auth_type="admin",
         )
-        await self.db.identities.create(
-            user["id"], port=_PORT_FOR_ROLE.get(req.role, "opc"), role=req.role,
-            sub_role=req.sub_role, org_id=req.org_id, region_id=req.region_id,
-            name=req.nickname or req.username,
-        )
         return user
 
     async def set_user_role(self, actor: dict, user_id: str, role: str, sub_role: str, org_id: str, region_id: str) -> dict: