fix(models): show version diff labels when locale JSON is stale

[akshaykumar2505]

Summary

• Version diff labels (Removed, Compare, Changes, ...) now fall back to English in the JS bundle, so a stale /locales/en/models.json cannot show raw �ersion_diff.* keys.
• Locale fetches skip HTTP cache, and nginx no longer SPA-fallbacks missing locale files to index.html.

Test plan

• Open Models versions after merge + client image + pod recreate
• Pink tag reads Removed (not �ersion_diff.removed)
• Compare / Changes / column headers are English words
• RU/ZH still use locale JSON when that language is selected