Add package structure and resource path utilities

- Created langbot/ package with __init__.py and __main__.py entry point
- Added paths utility to find frontend and resource files from package installation
- Updated config loading to use resource paths
- Updated frontend serving to use resource paths
- Added MANIFEST.in for package data inclusion
- Updated pyproject.toml with build system and entry points

Co-authored-by: RockChinQ <45992437+RockChinQ@users.noreply.github.com>

pkg/core/app.py

@@ -179,8 +179,12 @@ class Application:
 
     async def print_web_access_info(self):
         """Print access webui tips"""
+        
+        from ..utils import paths
+        
+        frontend_path = paths.get_frontend_path()
 
-        if not os.path.exists(os.path.join('.', 'web/out')):
+        if not os.path.exists(frontend_path):
             self.logger.warning('WebUI 文件缺失，请根据文档部署：https://docs.langbot.app/zh')
             self.logger.warning(
                 'WebUI files are missing, please deploy according to the documentation: https://docs.langbot.app/en'