Rename translation helper and consolidate frontend translation modules

[seebaer1976]

• Renames the frontend translation helper from frontend/src/panel/common/i18n.ts to translations.ts
• Moves language dictionaries into dedicated files under translations for en, de and it
• Updates all translation imports across the panel views and renderer editor to use the new helper path
• Improves naming clarity and makes multilingual support easier to maintain going forward

[studiobts]

Hi @seebaer1976, thanks for the PR and the effort put into it!

I'm currently heads-down working on the next major release which is coming out shortly, so I'm not in a position to properly review or merge this right now. I'll get back to it once the release is out.

Thanks for your patience!