remove Hugo artifacts

- Delete config.yaml (metadata ported to myst.yml in previous commit)
- Remove scientific-python-hugo-theme submodule (only consumed by Hugo;
  other SP repos vendor their own copy — ADR 0003)
- Drop .hugo* and resources/ from .gitignore; both are Hugo-specific.
  _build/ was already present; public/ kept for html-all output.

Author: lundybernard

.gitignore

@@ -1,6 +1,5 @@
-.hugo*
 *~
-resources/
 public/
 _build/
+content/_build/
 .DS_Store

.gitmodules

@@ -1,6 +1,3 @@
-[submodule "themes/scientific-python-hugo-theme"]
-	path = themes/scientific-python-hugo-theme
-	url = https://github.com/scientific-python/scientific-python-hugo-theme
 [submodule "external-content/cookie"]
 	path = external-content/cookie
 	url = https://github.com/scientific-python/cookie