✨ feat: 阶段 0 收尾——认证边界、请求上下文与垂直切片（WP-01 第 5-7 步）

- 认证：Web Session（__Host- Cookie、HttpOnly/Secure/SameSite=Lax、CSPRNG opaque token 数据库只存哈希）、CSRF 双提交、Origin 校验、dev 登录/登出端点；未认证 401、缺 CSRF 403
- 中间件：Hunjing-Request-ID 回显/生成（request_ UUIDv4）+ W3C traceparent 校验透传；JSON 结构化日志与敏感头脱敏
- 迁移 2：conversation/branch/message/run/idempotency_record 五表（含检查约束与复合索引）；Session 补 token/csrf 哈希列
- 垂直切片：POST /v1/conversations/{id}/messages 按 Idempotency-Key 幂等（同键同体 200 重放、异体 409），同事务原子写 Message+Run+Audit+Outbox+幂等记录；ContentBlock text/markdown 判别联合（未知类型 422）
- SSE：GET /v1/runs/{id}/events 返回快照与终止状态事件 envelope
- 测试 26 项全绿：IDOR 跨域 404 fail-closed、失败注入回滚无孤儿（Run 崩溃后 message/run/audit/outbox/幂等全零）、SSE 事件序、auth 边界；ruff/mypy strict 干净
- 修复真实问题：asyncpg 跨事件循环（anyio/pytest-asyncio 双 loop、模块级 engine 改为 app 实例持有）、httpx 拒存 http 下 Secure Cookie

backend/app/auth/dependencies.py

@@ -0,0 +1,56 @@
+"""认证依赖：当前用户解析与状态变更防护。"""
+
+from typing import Annotated
+
+from fastapi import Depends, Header, HTTPException, Request, status
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.auth.service import SESSION_COOKIE, resolve_session
+from app.db.session import get_db
+from app.models import User
+
+ALLOWED_ORIGINS: set[str] = set()  # 由配置注入；空集表示本地开发放行同源
+
+
+async def get_current_user(
+    request: Request,
+    db: Annotated[AsyncSession, Depends(get_db)],
+) -> User:
+    token = request.cookies.get(SESSION_COOKIE)
+    if token is None:
+        raise HTTPException(status.HTTP_401_UNAUTHORIZED, "未登录")
+    session = await resolve_session(db, token)
+    if session is None:
+        raise HTTPException(status.HTTP_401_UNAUTHORIZED, "会话无效或已过期")
+    user = await db.get(User, session.user_id)
+    if user is None:
+        raise HTTPException(status.HTTP_401_UNAUTHORIZED, "会话主体不存在")
+    # 请求级上下文供后续依赖使用（不重复查询）
+    request.state.session_id = session.id
+    request.state.session_csrf_hash = session.csrf_token_hash
+    return user
+
+
+async def require_state_change(
+    request: Request,
+    user: Annotated[User, Depends(get_current_user)],
+    hunjing_csrf_token: Annotated[str | None, Header(alias="Hunjing-CSRF-Token")] = None,
+) -> User:
+    """Cookie 状态变更：Origin 校验 + CSRF 双提交（契约 2.1 节）。"""
+    if ALLOWED_ORIGINS:
+        origin = request.headers.get("Origin")
+        if origin is not None and origin not in ALLOWED_ORIGINS:
+            raise HTTPException(status.HTTP_403_FORBIDDEN, "Origin 不被允许")
+    csrf_hash = getattr(request.state, "session_csrf_hash", None)
+    if csrf_hash is None or not _csrf_matches(csrf_hash, hunjing_csrf_token):
+        raise HTTPException(status.HTTP_403_FORBIDDEN, "CSRF 校验失败")
+    return user
+
+
+def _csrf_matches(expected_hash: str, provided: str | None) -> bool:
+    import hashlib
+    import secrets
+
+    if provided is None:
+        return False
+    return secrets.compare_digest(expected_hash, hashlib.sha256(provided.encode()).hexdigest())