feat: 增加差旅报销标准测算和财务终审流程

新增差旅报销测算接口及 Spreadsheet 规则解析，审批流程拆分
直属领导审批与财务终审两阶段并细分权限，修复 PDF 文本层
缺失时自动回退 OCR，提交后清理关联会话，前端适配审批流
交互并补充单元测试。

server/tests/test_ocr_service.py

@@ -177,3 +177,80 @@ def test_ocr_service_converts_pdf_to_images_and_returns_image_preview(
     assert any(field.label == "车次/航班" and field.value == "G1234" for field in recognized.document_fields)
     assert recognized.lines[0].page_index == 0
     assert recognized.lines[1].page_index == 1
+
+
+def test_ocr_service_prefers_pdf_text_layer_when_rendered_ocr_is_placeholder_heavy(
+    monkeypatch,
+    tmp_path: Path,
+) -> None:
+    def fake_convert_pdf_to_images(self, *, pdf_path: Path, output_dir: Path) -> list[Path]:
+        page = output_dir / "page-1.png"
+        page.write_bytes(b"fake-page")
+        return [page]
+
+    def fake_invoke_worker(
+        self,
+        *,
+        python_bin: str,
+        worker_path: str,
+        input_paths: list[Path],
+    ) -> dict:
+        return {
+            "engine": "paddleocr_mobile",
+            "model": "PP-OCRv5_mobile",
+            "documents": [
+                {
+                    "input_path": str(input_paths[0]),
+                    "engine": "paddleocr_mobile",
+                    "model": "PP-OCRv5_mobile",
+                    "text": "□□□□□□\n□□□□：26319166100006175398\nG456\n□□:□354.00",
+                    "summary": "□□□□□□；□□□□：26319166100006175398",
+                    "avg_score": 0.88,
+                    "line_count": 4,
+                    "page_count": 1,
+                    "warnings": [],
+                    "lines": [
+                        {
+                            "text": "□□□□□□",
+                            "score": 0.88,
+                            "box": [[1, 2], [10, 2], [10, 8], [1, 8]],
+                        }
+                    ],
+                }
+            ],
+        }
+
+    monkeypatch.setenv("STORAGE_ROOT_DIR", str(tmp_path / "storage"))
+    monkeypatch.setattr(OcrService, "_resolve_python_bin", lambda self: "python")
+    monkeypatch.setattr(OcrService, "_resolve_worker_path", lambda self: "worker.py")
+    monkeypatch.setattr(OcrService, "_convert_pdf_to_images", fake_convert_pdf_to_images)
+    monkeypatch.setattr(OcrService, "_invoke_worker", fake_invoke_worker)
+    monkeypatch.setattr(
+        OcrService,
+        "_extract_pdf_text_layer",
+        lambda self, pdf_path: (
+            "电子发票（铁路电子客票）\n"
+            "发票号码:26319166100006175398\n"
+            "上海虹桥站\n"
+            "武汉站\n"
+            "G456\n"
+            "票价:￥354.00"
+        ),
+    )
+    get_settings.cache_clear()
+    try:
+        result = OcrService().recognize_files(
+            [
+                ("train-ticket.pdf", b"%PDF-1.4 fake", "application/pdf"),
+            ]
+        )
+    finally:
+        get_settings.cache_clear()
+
+    recognized = result.documents[0]
+    assert "电子发票（铁路电子客票）" in recognized.text
+    assert "上海虹桥站" in recognized.text
+    assert "□□□□" not in recognized.summary
+    assert recognized.document_type == "train_ticket"
+    assert recognized.preview_kind == ""
+    assert recognized.preview_data_url == ""