feat: introduce WeKnora Lite edition with lightweight configuration and deployment

- Added a new `.env.lite.example` file for the Lite version, providing a minimal configuration template.
- Updated `.env.example` to remove deprecated variables and include new Docreader settings.
- Enhanced Docker configurations to support the Lite version, including a new Dockerfile for the Docreader service.
- Introduced a Makefile target for building and running the Lite version, along with packaging capabilities.
- Created GitHub workflows for building and releasing Lite binaries, including Homebrew formula support.
- Implemented a new service file for managing the Lite version as a system service.

This update enables a streamlined, single-binary deployment of WeKnora, reducing external dependencies and simplifying setup.

docreader/parser/pdf_parser.py

@@ -1,6 +1,5 @@
 from docreader.parser.chain_parser import FirstParser
 from docreader.parser.markitdown_parser import MarkitdownParser
-from docreader.parser.mineru_parser import MinerUParser
 
 
 class PDFParser(FirstParser):
@@ -13,4 +12,4 @@ class PDFParser(FirstParser):
     The first successful parser result will be returned.
     """
     # Parser classes to try in order (chain of responsibility pattern)
-    _parser_cls = (MinerUParser, MarkitdownParser)
+    _parser_cls = (MarkitdownParser,)