Scaffold site: nav, stub sections, contact/privacy/terms, styling

Adds top nav links to Books/Authors/Submissions stub pages, and
Contact/Privacy/Terms pages modeled on reground-site's structure. Contact
form posts to the already-provisioned eec-twosquirrelspress backend.
Styling implements the press's brand palette and font choices.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

content/submissions/_index.md

@@ -0,0 +1,6 @@
+---
+title: "Submissions"
+description: "How to submit work to Two Squirrels Press."
+---
+
+Coming soon.