Make setup ISO-only

Remove legacy online installer entrypoints, collapse migrations for 4.0, and move setup responsibilities into target-side system, hardware, and user commands.

install/user/git.sh

@@ -0,0 +1,8 @@
+# Set identification from install inputs
+if [[ -n ${OMARCHY_USER_NAME//[[:space:]]/} ]]; then
+  git config --global user.name "$OMARCHY_USER_NAME"
+fi
+
+if [[ -n ${OMARCHY_USER_EMAIL//[[:space:]]/} ]]; then
+  git config --global user.email "$OMARCHY_USER_EMAIL"
+fi