Allowlist aggregate order columns and template names

Page.aggregate interpolated order_by into SQL unchecked while
already allowlisting order_direction; the column is now normalized
and checked against the sortable columns, falling back to pages.id.
Its values arrive from editor-authored aggregate shortcodes, so
this was editor-gated, but the asymmetry was wrong regardless.

template_name and default_template_name now validate inclusion in
Page.custom_templates -- names render as filesystem paths, so only
names actually present in the template directory are acceptable.
Validated only on change: legacy rows whose template file has since
vanished stay saveable, and valid_template's render-time fallback
to standard_template continues to cover them. Two tests that wrote
fabricated template names through the front door now arrange their
state correctly (update_column for the stale-name fallback test, a
real template for the update-persists test).

0 files changed, 0 insertions, 0 deletions