```

refactor: 移除审批和回写功能模块

移除了整个审批(approvals)和官方回写(writebacks)功能模块，
包括相关模型、路由、服务和配置项。更新了数据库迁移文件，
删除了相关的审批请求表和官方回写运行表。同时从API路由器中
移除了相应的路由，并调整了安全常量和字段验证器以匹配变更。
```

alembic/versions/202607060002_approval_ticket_consumption.py

@@ -1,57 +1,19 @@
-"""Add approval ticket consumption fields.
+"""Remove obsolete approval ticket migration step.
 
 Revision ID: 202607060002
 Revises: 202607060001
 Create Date: 2026-07-06
 """
 
-from alembic import op
-import sqlalchemy as sa
-from sqlalchemy import inspect
-
-
 revision = "202607060002"
 down_revision = "202607060001"
 branch_labels = None
 depends_on = None
 
-APPROVAL_REQUESTS_TABLE = "approval_requests"
-USED_BY_COLUMN = "used_by"
-USED_AT_COLUMN = "used_at"
-
-
-def _column_names() -> set[str]:
-    inspector = inspect(op.get_bind())
-    return {
-        column["name"]
-        for column in inspector.get_columns(APPROVAL_REQUESTS_TABLE)
-    }
-
 
 def upgrade() -> None:
-    columns = _column_names()
-    if USED_BY_COLUMN not in columns:
-        op.add_column(
-            APPROVAL_REQUESTS_TABLE,
-            sa.Column(USED_BY_COLUMN, sa.String(length=128), nullable=True),
-        )
-        op.create_index(
-            op.f("ix_approval_requests_used_by"),
-            APPROVAL_REQUESTS_TABLE,
-            [USED_BY_COLUMN],
-            unique=False,
-        )
-    if USED_AT_COLUMN not in columns:
-        op.add_column(
-            APPROVAL_REQUESTS_TABLE,
-            sa.Column(USED_AT_COLUMN, sa.DateTime(), nullable=True),
-        )
+    pass
 
 
 def downgrade() -> None:
-    columns = _column_names()
-    if USED_BY_COLUMN in columns:
-        op.drop_index(op.f("ix_approval_requests_used_by"), table_name=APPROVAL_REQUESTS_TABLE)
-        op.drop_column(APPROVAL_REQUESTS_TABLE, USED_BY_COLUMN)
-    if USED_AT_COLUMN in columns:
-        op.drop_column(APPROVAL_REQUESTS_TABLE, USED_AT_COLUMN)
+    pass