feat(connect): add site-wide Connect row + weave Discord into "You're Early"

- SiteFooter: new "Connect" row driven by a SOCIAL_LINKS source-of-truth list
  (Discord, YouTube to start; trivial to extend). Self-contained brand SVGs,
  themed pills that work in light and dark. Also fixed the subnote em dash.
- You're Early: a short "there's a room for the early ones" beat inviting
  people into the Discord at the connect level, whether or not they install.