feat: persist draft messages and UI refinements

- Add dedicated draft-store with AsyncStorage persistence for drafts
  that survive app refresh/crash
- Reduce markdown bold weight from bold to medium (500)
- Various theme and component style updates
- Server bootstrap and config improvements

🤖 Generated with [Claude Code](https://claude.com/claude-code)

packages/app/src/components/headers/screen-header.tsx

@@ -35,7 +35,7 @@ export function ScreenHeader({ left, right, leftStyle, rightStyle }: ScreenHeade
 
 const styles = StyleSheet.create((theme) => ({
   header: {
-    backgroundColor: theme.colors.background,
+    backgroundColor: theme.colors.surface0,
   },
   inner: {},
   row: {