fix: replace sys.path.insert(0) with safe sys.path.append (issue #7)

- Append project root instead of inserting at position 0
- Prevents import shadowing of system packages
- Check for duplicates before adding to sys.path
- Add __init__.py to models package

main.py

@@ -8,8 +8,11 @@ import argparse
 import os
 import sys
 
-# Add the current directory to Python path
-sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))
+# Ensure project root is in path for direct execution (python main.py)
+# Use a set to avoid duplicates and don't insert at position 0 to avoid shadowing
+_project_root = os.path.dirname(os.path.abspath(__file__))
+if _project_root not in sys.path:
+    sys.path.append(_project_root)
 
 from cli.commands import handle_command
 from cli.parser import parse_args, print_help