Closes#43
Adds a new read-only endpoint to resolve a Silo item UUID to its full
ItemResponse. Used by silo-mod to resolve FreeCAD document SiloUUID
properties to part numbers during BOM sync.
- Reuses existing ItemRepository.GetByID() (items.id is the stable UUID)
- Returns 404 for archived items
- Registered in viewer-accessible route group (no editor role required)
