feat(expenses): add transactional expense case events

server/src/app/api/v1/endpoints/expense_cases.py

@@ -0,0 +1,42 @@
+from __future__ import annotations
+
+from typing import Annotated
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy.orm import Session
+
+from app.api.deps import CurrentUserContext, get_current_user, get_db
+from app.schemas.expense_case import ExpenseCaseTimelineRead
+from app.services.expense_cases import ExpenseCaseService
+from app.services.expense_claims import ExpenseClaimService
+
+router = APIRouter(prefix="/expense-cases")
+DbSession = Annotated[Session, Depends(get_db)]
+CurrentUser = Annotated[CurrentUserContext, Depends(get_current_user)]
+
+
+@router.get(
+    "/by-claim/{claim_id}",
+    response_model=ExpenseCaseTimelineRead,
+    summary="查询报销单所属费用事件时间线",
+    description="返回当前用户有权查看的费用事件、关联单据和结构化业务事件。",
+)
+def get_expense_case_by_claim(
+    claim_id: str,
+    db: DbSession,
+    current_user: CurrentUser,
+) -> ExpenseCaseTimelineRead:
+    claim = ExpenseClaimService(db).get_claim(claim_id, current_user)
+    if claim is None:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="费用单据不存在。")
+
+    expense_case = ExpenseCaseService(db).get_timeline_for_claim(
+        claim.id,
+        tenant_id=current_user.tenant_id,
+    )
+    if expense_case is None:
+        raise HTTPException(
+            status_code=status.HTTP_404_NOT_FOUND,
+            detail="该单据尚未纳入统一费用事件。",
+        )
+    return ExpenseCaseTimelineRead.model_validate(expense_case)