Gronkh.tv Kodi Addon - v2.0.0

Refactor plugin: modular code and support new v3 backend

Replace the old monolithic addon.py with a new main.py entry point and a collection of resources/lib modules (api, http, player, ui, utils, constants, playlist, storage) to modularize API access, playback, UI and utilities. Bump addon version to 2.0.0 and update addon.xml to use main.py, change repository/source and license to MIT. Update README with German descriptions and feature list. Remove legacy files and language PO files, and replace GPLv3 LICENSE with an MIT license.