refactor: move content under data/ for Git Sync compatibility

Git Sync expects folders: pages/themes/plugins/config/data
Content now at data/content/{fqdn}/pages/

Assisted-by: GLM-5 via Crush <crush@charm.land>

data/content/plan.ezpodstack.org/dev.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+mdbook \
+    serve \
+    . \
+    -p 3001 \
+    -d book \