feat: 新增文档模型类，调整配置与解析逻辑，优化日志及导入

移除日志设置与冗余代码，优化导入、类型提示及OCR后端管理
统一调整各文件模块导入路径为绝对导入
调整导入路径，移除部分导入，优化日志及注释
升级文档解析器为 Docx2Parser，优化超时与图片处理逻辑

docreader/parser/markitdown_parser.py

@@ -0,0 +1,31 @@
+import io
+import logging
+
+from markitdown import MarkItDown
+
+from docreader.models.document import Document
+from docreader.parser.base_parser import BaseParser
+from docreader.parser.chain_parser import PipelineParser
+from docreader.parser.markdown_parser import MarkdownParser
+
+logger = logging.getLogger(__name__)
+
+
+class StdMarkitdownParser(BaseParser):
+    """
+    PDF Document Parser
+
+    This parser handles PDF documents by extracting text content.
+    It uses the markitdown library for simple text extraction.
+    """
+
+    def __init__(self, *args, **kwargs):
+        self.markitdown = MarkItDown()
+
+    def parse_into_text(self, content: bytes) -> Document:
+        result = self.markitdown.convert(io.BytesIO(content), keep_data_uris=True)
+        return Document(content=result.text_content)
+
+
+class MarkitdownParser(PipelineParser):
+    _parser_cls = (StdMarkitdownParser, MarkdownParser)