[document_repository] Fix swal translation coverage

[arnav-makkar]

Brief summary of changes

This PR fixes untranslated document_repository swal dialogs by removing hardcoded English text, correcting a namespace mismatch, and localizing known backend error messages shown in popups.

• Updated add-category, delete-category, edit-entry, and delete-file swals to use t(...) translations.
• Fixed delete confirmation text lookup by switching "You won't be able to revert this!" to the document_repository namespace.
• Added translation mapping for known backend errors (Duplicate category name under same parent folder., Can not delete non-empty category) with raw-text fallback for unknown messages.
• Added missing translation keys and entries for fr, hi, and ja (with English msgid fallback), including Delete and category error strings.
• Added translated OK confirm button text in the affected swals.

Since I don't have experience with Japanese, a strict review will be required for its translations.
Please let me know whatever changes required and I'll incorporate them.

Screenshots

Link(s) to related issue(s)

• Resolves [document_repository] Swals not translated #10280 [document_repository] some untranslated error and confirmations messages. #10215