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>

alembic/versions/0014_drop_user_identities.py

@@ -0,0 +1,39 @@
+"""去多身份：drop user_identities
+
+Revision ID: 0014_drop_user_identities
+Revises: 0013_opc_cert_park_transfer
+Create Date: 2026-08-26
+"""
+from __future__ import annotations
+
+from alembic import op
+
+revision = "0014_drop_user_identities"
+down_revision = "0013_opc_cert_park_transfer"
+branch_labels = None
+depends_on = None
+
+
+def upgrade() -> None:
+    # 账号单一角色（去多身份/多端口）：user_identities 不再使用，删除表。
+    op.drop_table("user_identities")
+
+
+def downgrade() -> None:
+    # 降级：重建 user_identities（结构由模型决定，这里按原 models 恢复）。
+    import sqlalchemy as sa
+
+    op.create_table(
+        "user_identities",
+        sa.Column("id", sa.String(), primary_key=True),
+        sa.Column("user_id", sa.String(), sa.ForeignKey("users.id", ondelete="CASCADE"), nullable=False),
+        sa.Column("port", sa.String(), default="opc"),
+        sa.Column("role", sa.String(), default="opc_member"),
+        sa.Column("sub_role", sa.String(), nullable=True),
+        sa.Column("name", sa.String(), default=""),
+        sa.Column("org_id", sa.String(), sa.ForeignKey("organizations.id"), nullable=True),
+        sa.Column("region_id", sa.String(), sa.ForeignKey("regions.id"), nullable=True),
+        sa.Column("status", sa.String(), default="active"),
+        sa.Column("created_at", sa.String(), default=""),
+        sa.Column("updated_at", sa.String(), default=""),
+    )