- Replace multiple action buttons with unified InsertMenu dropdown
- Consolidate upload, link memo, and location into single + button
- Redesign VisibilitySelector with text-based dropdown UI
- Unify badge styling for location, attachments, and links
  - Consistent height (h-7), padding, gaps, and border styles
  - Secondary foreground text color with hover states
  - Max width with truncation for long content
- Add image thumbnails in attachment badges
- Simplify button hierarchy with ghost variant for save/cancel
- Remove obsolete components (TagSelector, MarkdownMenu, etc.)
- Extract LocationView to separate component for better organization

Fixes #5196