`loadInitial()` fetched 100 messages while `_page_size` was 20,
so `_has_more` turned false too early and history stopped around
10h back. `loadMore()` also used `_currentPage * _page_size`
for offset, causing duplicates.
Use `_page_size` for initial load and rely on current message
count as offset. This removes `_currentPage` entirely and lets
older messages load correctly.
Signed-off-by: Texas0295 <kimura@texas0295.top>
7b238f32fd