Introduce .editorconfig #91
Description
Imported from tasks.yml (id: 405).\n\nDescription: Add a basic .editorconfig enforcing UTF-8, newline at EOF, and 4-space indentation.\n\nActionable Steps:\n- Create .editorconfig in repo root\n- Align with existing Python style (PEP8)\n- Document pre-commit hook idea in CONTRIBUTING\n\nAcceptance Criteria:\n- .editorconfig committed\n- Editors pick up settings automatically