[FEAT] Translation and i8n

[NeonDaniel]

Objective

Update the application to better scale to support more languages.

Initial Implementation Requirements

• Define a method/structure for per-language configuration files
• Define a UI element and/or browser-advertised language to select a language
• Define a structure for translated UI elements (onboarding guide, button labels, etc)

Other Considerations

• Currently, configuration drives a lot of language-specific parameters, such as UI elements, advisor names, and persona prompts, but some text is hard-coded in the backend and frontend modules
• Current config structure may be extended to contain locale-specific subdirectories; consider fallback to en for backwards-compat.
• Consider how to handle a request for an unsupported language
• Consider automation to generate translated resources for a target language

[NeonDaniel]

For front-end we can maintain a set of JSON files, one per language that maps en strings -> translated strings.

For back-end, we can maintain separate configuration files per-language. For personas, compare prompted response with english sys prompt vs translated system prompt in desired response language (possibly no changes necessary).
For back-end, we can extract strings from the config file that are to be translated and store those in the same or similar format to the front-end resources.

Main open discussion is regarding the translation source of truth, support for updating/correcting translations, and how/if we should manage translation at runtime