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/utils/paths.py

@@ -0,0 +1,73 @@
+"""Utility functions for finding package resources"""
+import os
+import sys
+from pathlib import Path
+
+
+def get_frontend_path() -> str:
+    """
+    Get the path to the frontend build files.
+    
+    Returns the path to web/out directory, handling both:
+    - Development mode: running from source directory
+    - Package mode: installed via pip/uvx
+    """
+    # First, check if we're running from source directory
+    # (main.py exists in current directory)
+    if os.path.exists('main.py') and os.path.exists('web/out'):
+        with open('main.py', 'r', encoding='utf-8') as f:
+            content = f.read()
+            if 'LangBot/main.py' in content:
+                return 'web/out'
+    
+    # Second, check if we're in a development/source directory
+    # (current directory has web/out)
+    if os.path.exists('web/out'):
+        return 'web/out'
+    
+    # Third, try to find it relative to this file's location
+    # This handles the case when installed as a package
+    pkg_dir = Path(__file__).parent.parent.parent
+    frontend_path = pkg_dir / 'web' / 'out'
+    if frontend_path.exists():
+        return str(frontend_path)
+    
+    # Fourth, check if it's in the package installation directory
+    # Look for the web/out directory in the sys.path
+    for path in sys.path:
+        candidate = Path(path) / 'web' / 'out'
+        if candidate.exists():
+            return str(candidate)
+    
+    # Return the default path (will be checked by caller)
+    return 'web/out'
+
+
+def get_resource_path(resource: str) -> str:
+    """
+    Get the path to a resource file.
+    
+    Args:
+        resource: Relative path to resource (e.g., 'templates/config.yaml')
+    
+    Returns:
+        Absolute path to the resource
+    """
+    # First, check if resource exists in current directory
+    if os.path.exists(resource):
+        return resource
+    
+    # Second, try to find it relative to package directory
+    pkg_dir = Path(__file__).parent.parent.parent
+    resource_path = pkg_dir / resource
+    if resource_path.exists():
+        return str(resource_path)
+    
+    # Third, check in sys.path
+    for path in sys.path:
+        candidate = Path(path) / resource
+        if candidate.exists():
+            return str(candidate)
+    
+    # Return the original path
+    return resource