Layout: Display attribute editing per property

[JeroenDeDauw]

Follows-up to #692

Add per-property display attribute editing in the Layout editor. Each shown property would get a settings icon that opens a popover/dialog with type-specific display attribute fields.

Currently only Number has a display attribute (precision). This becomes more valuable as more property types with display attributes are added.

Context: the NeoWiki codebase, ADR 018, and investigation of the PropertyType display attribute system.
_{Written by Claude Code, Opus 4.6}

[krabina]

We should probably for now at least enable something like

• Has preferred property label
• Has property description
  both possible to add a language specification.

[JeroenDeDauw]

@krabina that goes beyond the scope of this task. I created a dedicated issue at #710