feat: 重构报销单服务并完善前端提交与审核交互

重构 expense_claims 服务模块结构并优化差旅票据审核逻辑，
增强用户代理服务的票据类型识别，前端报销创建页面拆分为
附件模型和会话模型模块，重构提交编排器和草稿关联确认流
程，更新知识库索引，补充单元测试。

server/tests/test_expense_claim_service.py

@@ -136,7 +136,9 @@ def test_save_or_submit_preview_does_not_create_claim_without_explicit_action()
 
         assert result["preview_only"] is True
         assert result["status"] == "preview"
-        assert "差旅费按“交通票据金额 + 住宿标准 × 出差天数 + 出差补贴 × 出差天数”估算" in result["message"]
+        assert "报销测算参考：" in result["message"]
+        assert "| 项目 | 当前信息 | 复核口径 |" in result["message"]
+        assert "交通票据金额 + 住宿标准" not in result["message"]
         assert _count_claims(db) == before_count
 
 
@@ -598,6 +600,91 @@ def test_upsert_draft_from_ontology_supports_link_or_create_for_multi_documents(
         assert float(new_claim.amount) == 50.5
 
 
+def test_link_existing_draft_blocks_duplicate_uploaded_invoice() -> None:
+    user_id = "duplicate@example.com"
+
+    with build_session() as db:
+        employee = Employee(
+            employee_no="E5010",
+            name="重复票据员工",
+            email=user_id,
+        )
+        db.add(employee)
+        db.flush()
+        existing_claim = ExpenseClaim(
+            claim_no="EXP-202605-021",
+            employee_id=employee.id,
+            employee_name="重复票据员工",
+            department_name="销售部",
+            project_code=None,
+            expense_type="transport",
+            reason="原有交通报销",
+            location="上海",
+            amount=Decimal("32.50"),
+            currency="CNY",
+            invoice_count=1,
+            occurred_at=datetime(2026, 5, 13, tzinfo=UTC),
+            status="draft",
+            approval_stage="待提交",
+            risk_flags_json=[],
+        )
+        existing_claim.items = [
+            ExpenseClaimItem(
+                claim_id=existing_claim.id,
+                item_date=date(2026, 5, 13),
+                item_type="transport",
+                item_reason="原有交通报销",
+                item_location="上海",
+                item_amount=Decimal("32.50"),
+                invoice_id="didi-trip.png",
+            )
+        ]
+        db.add(existing_claim)
+        db.commit()
+
+        context_json = {
+            "name": "重复票据员工",
+            "review_action": "link_to_existing_draft",
+            "draft_claim_id": existing_claim.id,
+            "attachment_names": ["didi-trip.png"],
+            "attachment_count": 1,
+            "ocr_documents": [
+                {
+                    "filename": "didi-trip.png",
+                    "summary": "滴滴出行 支付金额 32.50 元",
+                    "text": "滴滴出行 支付金额 32.50 元",
+                    "document_type": "taxi_receipt",
+                    "scene_code": "transport",
+                    "document_fields": [{"key": "amount", "label": "支付金额", "value": "32.50"}],
+                }
+            ],
+        }
+        ontology = SemanticOntologyService(db).parse(
+            OntologyParseRequest(
+                query="把这张票据关联到已有草稿",
+                user_id=user_id,
+                context_json=context_json,
+            )
+        )
+
+        result = ExpenseClaimService(db).upsert_draft_from_ontology(
+            run_id=ontology.run_id,
+            user_id=user_id,
+            message="把这张票据关联到已有草稿",
+            ontology=ontology,
+            context_json=context_json,
+        )
+
+        db.refresh(existing_claim)
+        assert result["duplicate_attachment_blocked"] is True
+        assert result["submission_blocked"] is True
+        assert "重复" in result["message"]
+        assert "重新上传不同的票据" in result["message"]
+        assert len(existing_claim.items) == 1
+        assert existing_claim.invoice_count == 1
+        assert float(existing_claim.amount) == 32.5
+
+
 def test_upsert_travel_draft_uses_ticket_item_types_and_auto_allowance() -> None:
     user_id = "travel-allowance@example.com"