Add local .logan/ persistence and activity history panel

Store per-file bookmarks, highlights, and activity history in .logan/<file>.json
sidecar files next to analyzed files instead of monolithic ~/.logan/ stores.
Lazy migration moves existing data from global to local on first open, with
read-only directory fallback. New History panel (Ctrl+7) shows reverse-
chronological activity log with date grouping, category filtering, and
clickable entries.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: ozgesolidkey