Convert 6 blog settings pages (settings-home, cache, snippets, menu-items,
tag-groups, tag-group-edit) from Python page helpers to .sx defpages with
(service "blog-page" ...) IO primitives. Create data-driven defcomps that
handle iteration via (map ...) instead of Python loops.
Post-related page helpers (editor, post-admin/data/preview/entries/settings/edit)
remain as Python helpers — they depend on _ensure_post_data and sx_components
rendering functions that need separate conversion.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>