[meramsey]

Summary

• Remove the app-side 10,000-character composer limit so long prompts are preserved and the server decides whether a prompt is acceptable.
• Add an opt-in Message timestamps setting (off by default) and display each message's local date/time using the selected app locale.
• Preserve settings migrations by defaulting the new preference off for existing installs.

Validation

• npm test (385 passing)
• npm run typecheck
• npm run check:versions
• git diff --check

This is intentionally limited to prompt length and per-message timestamps; it does not change Android package identity or add a separate build variant.