feat: 拆分 usage 记录的请求体/响应体为客户端侧与提供商侧

将 request_body/response_body 语义明确为客户端原始请求体和提供商原始响应体，
新增 provider_request_body（格式转换后发给提供商的请求体）和 client_response_body
（格式转换后返回给客户端的响应体），支持跨格式转换场景下分别查看两侧数据。

- 数据库新增 provider_request_body/client_response_body 及对应压缩字段
- 全链路（telemetry/recording/handler/stream_context）传递新字段
- 维护调度器同步支持新字段的压缩与清理
- 前端请求详情抽屉支持请求体/响应体/响应头的客户端/提供商视图切换

alembic/versions/20260220_1800_7e8f9a0b1c2d_add_provider_request_body_and_client_response_body.py

@@ -0,0 +1,56 @@
+"""Add provider_request_body and client_response_body columns to usage table
+
+Revision ID: 7e8f9a0b1c2d
+Revises: 6d7e8f9a0b1c
+Create Date: 2026-02-20 18:00:00.000000
+
+"""
+
+from __future__ import annotations
+
+from collections.abc import Sequence
+
+import sqlalchemy as sa
+from sqlalchemy import inspect
+
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "7e8f9a0b1c2d"
+down_revision: str | None = "6d7e8f9a0b1c"
+branch_labels: str | Sequence[str] | None = None
+depends_on: str | Sequence[str] | None = None
+
+
+def upgrade() -> None:
+    conn = op.get_bind()
+    inspector = inspect(conn)
+    existing_columns = {col["name"] for col in inspector.get_columns("usage")}
+
+    if "provider_request_body" not in existing_columns:
+        op.add_column("usage", sa.Column("provider_request_body", sa.JSON(), nullable=True))
+    if "provider_request_body_compressed" not in existing_columns:
+        op.add_column(
+            "usage", sa.Column("provider_request_body_compressed", sa.LargeBinary(), nullable=True)
+        )
+    if "client_response_body" not in existing_columns:
+        op.add_column("usage", sa.Column("client_response_body", sa.JSON(), nullable=True))
+    if "client_response_body_compressed" not in existing_columns:
+        op.add_column(
+            "usage", sa.Column("client_response_body_compressed", sa.LargeBinary(), nullable=True)
+        )
+
+
+def downgrade() -> None:
+    conn = op.get_bind()
+    inspector = inspect(conn)
+    existing_columns = {col["name"] for col in inspector.get_columns("usage")}
+
+    for col in (
+        "client_response_body_compressed",
+        "client_response_body",
+        "provider_request_body_compressed",
+        "provider_request_body",
+    ):
+        if col in existing_columns:
+            op.drop_column("usage", col)