Editable install fails due to missing LICENSE file and ambiguous package discovery #225

Running pip install -e . fails with the following issues:

1. Missing or misnamed license file

   File '.../PDF-Extract-Kit/LICENSE' cannot be found
   

   This is caused by the line license = { file = "LICENSE" } in pyproject.toml, but no such file exists.

   Fix: Change to a valid existing file (e.g., LICENSE.md) or replace with a license string

2. Multiple top-level packages discovered

   Multiple top-level packages discovered in a flat-layout: ['assets', 'configs', 'project', 'pdf_extract_kit']
   

   This prevents setuptools from building the project in editable mode.

   Fix: Add explicit package inclusion

These changes are required to successfully install the package in editable mode using pip install -e ..