Change default edge and vertex color from near-black RGB(25,25,25)
to Catppuccin Mocha Subtext0 RGB(166,173,200) — a neutral light
blue-grey with 4.94:1 contrast against the Mocha background.
Update both the compile-time default in ViewParams.h and the
KindredCreate preference pack. The previous purple (#9344ee) had
only 2.91:1 contrast, causing edges to blend into the background
on cylindrical geometry.
Closes#196