Add Pro sidebar link and split nav wordmarks into icon + word

Add a "Pro" link at the bottom of the sidebar: a green rocket icon
(reused from moq/doc) plus a white "Pro" wordmark (derived from the
moq-pro logo). It points to pro.moq.dev on live and pro.moq.wtf on
staging, switched via import.meta.env.MODE.

To support an icon-only hover effect, split each combined nav wordmark
(demo/blog/docs/github/discord) into separate `-icon` and `-word` SVGs.
Each path keeps its original coordinates; only the viewBox is cropped,
so the artwork is pixel-identical. Every nav icon now rotates -6deg on
hover (group-hover:-rotate-6) while its word stays put.

Also recenter the Discord viewBox (its source art sat high in the
canvas, leaving a gap before Pro) so the column has even spacing.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: kixelated