refactor: 统一代码格式，调整多行代码换行风格

对多个文件进行代码格式化调整，将长行参数拆分为多行书写，提升代码可读性，包括：
- 调整函数定义、调用的多行换行格式
- 优化列表、元组、字典的多行排版
- 新增README.md项目说明文档

tests/test_file_parser.py

@@ -14,7 +14,13 @@ from app.core.file_parser import parse_file, supported_extensions
 def _make_minimal_pdf(text: str = "Hello PDF World") -> bytes:
     """构造一个含一页文本的最小 PDF（pypdf 可读出文本）"""
     content_stream = f"BT /F1 24 Tf 100 700 Td ({text}) Tj ET".encode("latin-1")
-    content_obj = b"<< /Length " + str(len(content_stream)).encode() + b" >>\nstream\n" + content_stream + b"\nendstream"
+    content_obj = (
+        b"<< /Length "
+        + str(len(content_stream)).encode()
+        + b" >>\nstream\n"
+        + content_stream
+        + b"\nendstream"
+    )
     return (
         b"%PDF-1.0\n"
         b"1 0 obj\n<< /Type /Catalog /Pages 2 0 R >>\nendobj\n"
@@ -36,6 +42,7 @@ def _make_minimal_pdf(text: str = "Hello PDF World") -> bytes:
 
 def _make_docx(text_lines: list[str]) -> bytes:
     from docx import Document  # type: ignore[import-untyped]
+
     document = Document()
     for line in text_lines:
         document.add_paragraph(line)
@@ -222,7 +229,9 @@ def _patch_pdf_ocr_deps(monkeypatch: pytest.MonkeyPatch) -> None:
     monkeypatch.setitem(sys.modules, "rapidocr_onnxruntime", fake_module)
 
 
-def test_parse_pdf_ocr_fallback_when_text_layer_empty(monkeypatch: pytest.MonkeyPatch) -> None:
+def test_parse_pdf_ocr_fallback_when_text_layer_empty(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
     """扫描件 PDF（文本层全空）触发 OCR 降级，返回识别文本"""
     _patch_pdf_ocr_deps(monkeypatch)
     monkeypatch.setattr(settings, "pdf_ocr_enabled", True)
@@ -256,7 +265,9 @@ def test_parse_pdf_ocr_respects_max_pages(monkeypatch: pytest.MonkeyPatch) -> No
     assert "OCR文本第2页" not in result
 
 
-def test_parse_pdf_ocr_returns_empty_when_dependency_unavailable(monkeypatch: pytest.MonkeyPatch) -> None:
+def test_parse_pdf_ocr_returns_empty_when_dependency_unavailable(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
     """rapidocr 导入失败：降级返回空文本，且把 _ocr_unavailable 置 True 避免重试"""
     monkeypatch.setattr("pypdf.PdfReader", _FakePdfReader)
     # 故意让 rapidocr_onnxruntime 提供一个非类的 RapidOCR，构造时抛错
@@ -273,7 +284,9 @@ def test_parse_pdf_ocr_returns_empty_when_dependency_unavailable(monkeypatch: py
     assert fp_module._ocr_unavailable is True
 
 
-def test_parse_pdf_ocr_runtime_exception_falls_back_to_empty(monkeypatch: pytest.MonkeyPatch) -> None:
+def test_parse_pdf_ocr_runtime_exception_falls_back_to_empty(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
     """OCR 运行时抛错：仅告警，降级返回空文本（不抛出 ValueError）"""
     monkeypatch.setattr("pypdf.PdfReader", _FakePdfReader)
 
@@ -291,7 +304,9 @@ def test_parse_pdf_ocr_runtime_exception_falls_back_to_empty(monkeypatch: pytest
     assert parse_file("scan.pdf", b"fake pdf bytes") == ""
 
 
-def test_parse_pdf_text_layer_present_skips_ocr(monkeypatch: pytest.MonkeyPatch) -> None:
+def test_parse_pdf_text_layer_present_skips_ocr(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
     """文本层非空：直接返回文本，OCR 引擎不会被实例化"""
     call_count = 0