fix: reliable scroll-to-bottom, keyboard-aware project picker

- MessageList: use onContentSizeChange with bulk-scroll flag instead of
  fixed timers. Flag set on bulk load (delta > 1), cleared after 3s.
  Every content size change during that window scrolls to bottom.
- SessionDrawer: track keyboard height via keyboardWillShow/Hide events,
  apply as paddingBottom on drawer content. Scroll picker to end on
  TextInput focus. Removed KeyboardAvoidingView (doesn't work with
  absolute positioning).

	components/SessionDrawer.tsx	diff | view | blame | history
	components/chat/MessageList.tsx	diff | view | blame | history