Multi-language save fix:
- MultiSelect.svelte: selected prop changed to $bindable([])
(without $bindable, bind:selected never propagated to parent component,
so target_languages always stayed as default ['en'])
Target table column mapping (INSERT enhancement):
- target_language_column — stores language code (e.g. 'ru', 'en')
- target_source_column — stores original source text
- target_source_language_column — stores detected BCP-47 source language
- SQL generator includes these columns in INSERT when configured
- Frontend: 4 input fields under 'Target Column Mapping' section
with clear labels, placeholders, and i18n hints
Backend: model, schema, service, orchestrator
Frontend: job config page, i18n en+ru
DB: 3 new columns added to production