[Frontend] i18n.config.ts has no fallback when a locale JSON file fails to load

[grantfox-oss]

Join our community: https://t.me/+DOylgFv1jyJlNzM0

Why this matters
frontend/i18n.config.ts dynamically imports the messages file for a locale with no try/catch. If a locale segment resolves to a value outside en, es, tl, or the file is missing or malformed, the import throws unhandled and the request errors instead of falling back to English.

Acceptance criteria

• Wrap the dynamic import in a try/catch
• Fall back to frontend/messages/en.json on failure
• Add a unit test covering the fallback path

Files to touch

• frontend/i18n.config.ts

Out of scope
Adding new locales.