feat: expand ISO 639-1 language mapping to 23 EU languages

refactor: remove csv_for_anki.py, update docs for apkg_export

feat: add apkg_export.py with genanki-based .apkg export

refactor: remove deprecated apkg_generator module and tests

feat: add csv_for_anki module with helpers and core export function

fix: retry with apkg export files

feat: add APKG generate_apkg_package end-to-end function

feat: add APKG media injection with MD5 hashing and deduplication

feat: add APKG package generation with genanki and deck naming

feat: add APKG note creation with HTML escaping and media references

feat: add APKG model creation with genanki

refactor: flatten export folder and rename media files with meaningful names

feat: implement csv_export with zip download support and tests

restructure: move app.py to root, replace model submodules with HF Hub download script, add package markers

feat: scaffold repo structure with empty files and headers