fix: 补充 __init__.py 导出符号，修复测试导入错误

- src/core/extraction/__init__.py: 导出 _image_to_base64
- src/core/matching/__init__.py: 导出所有内部函数（_build_invoice_summary, _build_payment_records, _invoices_to_records, _match, _match_by_filename, _match_one_to_many, _match_one_to_one, _relative_tolerance, _safe_float）
- src/infra/documents/__init__.py: 导出 INVOICE_LEVEL_COLUMNS, PAYMENT_RECORD_COLUMNS
- tests/test_extractor.py: 修正 monkeypatch 路径为模块级引用

src/core/extraction/__init__.py

@@ -11,6 +11,7 @@ from .extractor import (
 )
 from .llm_extractor import (
     CACHE_DIR_NAME,
+    _image_to_base64,
     build_extraction_user_message,
     extract_document,
     extract_normal_info,
@@ -25,6 +26,7 @@ from .llm_extractor import (
 
 __all__ = [
     "CACHE_DIR_NAME",
+    "_image_to_base64",
     "build_extraction_user_message",
     "extract_document",
     "extract_normal_info",

src/core/matching/__init__.py

@@ -3,6 +3,28 @@
 提供发票与支付记录的金额匹配功能。
 """
 
-from .matcher import match_invoices_to_cards
+from .matcher import (
+    _build_invoice_summary,
+    _build_payment_records,
+    _invoices_to_records,
+    _match,
+    _match_by_filename,
+    _match_one_to_many,
+    _match_one_to_one,
+    _relative_tolerance,
+    _safe_float,
+    match_invoices_to_cards,
+)
 
-__all__ = ["match_invoices_to_cards"]
+__all__ = [
+    "_build_invoice_summary",
+    "_build_payment_records",
+    "_invoices_to_records",
+    "_match",
+    "_match_by_filename",
+    "_match_one_to_many",
+    "_match_one_to_one",
+    "_relative_tolerance",
+    "_safe_float",
+    "match_invoices_to_cards",
+]