docs(index): list Services alongside Hardware on the home page

Sidebar nav had Services after the previous commit, but the home page
body still only mentioned Hardware and House rules. Add a matching
bullet so visitors land somewhere obvious.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/index.md

@@ -8,6 +8,9 @@ jam-session community focused on self-hosted, open-source infrastructure.
 
 - [Hardware](hardware/index.md) — every machine in the lab, auto-indexed from per-host
   frontmatter blocks. Use this when planning where to deploy a new service.
+- [Services](services/index.md) — the things we run on (or around) that
+  hardware: the docs site, slides, Forgejo, DNS, the slide-builder
+  toolchain, and so on.
 - [House rules](house-rules.md) — working norms, governance, and
   what we do (and don't) do.