#19208: fix(android): auto-capitalize first letter in chat input

## Summary - Adds `KeyboardOptions(capitalization = KeyboardCapitalization.Sentences)` to the chat input `TextField`, so the keyboard starts with a capital letter at the beginning of each sentence — matching standard messaging app behavior. ## AI Disclosure - [x] AI-assisted (ClaudeCode via OpenClaw) — human reviewed and tested - [x] I understand what this code does ## Testing - Lightly tested on OnePlus 12 (Android 15) - Verified keyboard opens with uppercase at start of input ## Screenshots  🤖 Generated with [Claude Code](https://claude.com/claude-code)