MobLog

- Added on-demand rendering for the mob list: only visible rows and a small scroll buffer are prepared.
- Reuses list rows while scrolling, reducing the number of UI frames needed for large collections.
- Scrolling now updates the visible rows without rebuilding the entire NPC list.
- Loads portraits as needed and skips queued model requests for rows that are no longer visible or have been reused for another NPC.
- Cancelled portrait requests can load again when the NPC returns to view.
- Item-to-mob navigation still selects and scrolls to the correct entry, including NPCs outside the initial viewport.

Search, sorting and filters continue to use your full collection. Existing records and statistics are preserved.