Replace CrowdIn with a simpler translation system

[mikkohei13]

Discussion 6/2026 at https://luomus-ict.slack.com/archives/CQEQSQCP7/p1780404008552589

As a developer, I want to

• Have a system that handles translations relibale without excess work.

As a translator, I want to

• Find a string based on any language partial search (must)
• Find untranslated strings in any language (must)
• Easily handle syncing from and to GitHub, without mistakes (must)
• Have approval process for translations, i.e. have two statuses for each string: translated and translated+reviewed (must)
• Set a string as outdated. (Example: developer updates Finnish and English string, but cannot do Swedish translation, so they leave Swedish as it is. Others should be able to see and find strings that are outdated in this way.)
• Keep track of term translations (should)
• Be able to edit all language versions of a term at onec, without having to click aroun on the UI. (should)
• View history of translations for a given string: how it was and when it was changed (nice)
• Have AI-generated translations (nice?)
• Add information about where the string is used (should)