feat(server): 重构报销单服务，优化费用报销流程和数据校验逻辑，包含schema定义和服务实现

server/tests/test_reimbursement_endpoints.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import base64
 from collections.abc import Generator
 from datetime import UTC, date, datetime
 from decimal import Decimal
@@ -165,9 +166,18 @@ def test_claim_item_attachment_upload_preview_and_delete(monkeypatch, tmp_path)
     assert meta_response.status_code == 200
     meta_payload = meta_response.json()
     assert meta_payload["media_type"] == "image/png"
+    assert meta_payload["preview_kind"] == "image"
+    assert meta_payload["preview_url"].endswith(f"/reimbursements/claims/{claim_id}/items/{item_id}/attachment/preview")
     assert meta_payload["analysis"]["headline"]
     assert meta_payload["document_info"]["fields"][0]["label"] == "金额"
 
+    preview_response = client.get(
+        f"/api/v1/reimbursements/claims/{claim_id}/items/{item_id}/attachment/preview",
+        headers=headers,
+    )
+    assert preview_response.status_code == 200
+    assert preview_response.content == file_bytes
+
     content_response = client.get(
         f"/api/v1/reimbursements/claims/{claim_id}/items/{item_id}/attachment",
         headers=headers,
@@ -279,6 +289,67 @@ def test_claim_item_attachment_upload_flags_non_invoice_image_as_high_risk(monke
     assert any("附件内容" in point for point in analysis["points"])
 
 
+def test_claim_item_pdf_attachment_preview_returns_generated_image(monkeypatch, tmp_path) -> None:
+    preview_bytes = b"fake-preview-png"
+    preview_data_url = f"data:image/png;base64,{base64.b64encode(preview_bytes).decode('ascii')}"
+
+    def fake_recognize(
+        self,
+        files: list[tuple[str, bytes, str | None]],
+    ) -> OcrRecognizeBatchRead:
+        return OcrRecognizeBatchRead(
+            total_file_count=1,
+            success_count=1,
+            documents=[
+                OcrRecognizeDocumentRead(
+                    filename="invoice.pdf",
+                    media_type="application/pdf",
+                    text="滴滴出行电子发票 金额13.4元",
+                    summary="识别到交通票据，金额 13.4 元。",
+                    avg_score=0.96,
+                    line_count=1,
+                    page_count=1,
+                    document_type="taxi_receipt",
+                    document_type_label="出租车/网约车票据",
+                    scene_code="transport",
+                    scene_label="交通票据",
+                    preview_kind="image",
+                    preview_data_url=preview_data_url,
+                    warnings=[],
+                )
+            ],
+        )
+
+    monkeypatch.setattr(OcrService, "recognize_files", fake_recognize)
+    monkeypatch.setattr(ExpenseClaimService, "_get_attachment_storage_root", lambda self: tmp_path)
+
+    client, session_factory = build_client()
+    with session_factory() as db:
+        claim, item = seed_claim(db)
+        claim_id = claim.id
+        item_id = item.id
+
+    headers = {"x-auth-username": "emp-1", "x-auth-name": "Zhang San"}
+    upload_response = client.post(
+        f"/api/v1/reimbursements/claims/{claim_id}/items/{item_id}/attachment",
+        headers=headers,
+        files=[("file", ("invoice.pdf", b"%PDF-1.4 fake", "application/pdf"))],
+    )
+
+    assert upload_response.status_code == 200
+    meta_payload = upload_response.json()["attachment"]
+    assert meta_payload["preview_kind"] == "image"
+    assert meta_payload["preview_url"].endswith(f"/reimbursements/claims/{claim_id}/items/{item_id}/attachment/preview")
+
+    preview_response = client.get(
+        f"/api/v1/reimbursements/claims/{claim_id}/items/{item_id}/attachment/preview",
+        headers=headers,
+    )
+    assert preview_response.status_code == 200
+    assert preview_response.headers["content-type"].startswith("image/png")
+    assert preview_response.content == preview_bytes
+
+
 def test_claim_item_delete_removes_item_and_attachment(monkeypatch, tmp_path) -> None:
     def fake_recognize(
         self,