fix(rls): members_update WITH CHECK mirrors USING (D8)

UPDATE policy was USING-only: a privileged caller could mutate a member
row into a space they don't administer (no post-image re-check).
Migration 043 adds the mirrored WITH CHECK. Self column escalation
(space_id/role/status) remains blocked by the trigger (D9). Schema +
DB maps updated.

scripts/043_members_update_with_check.sql

@@ -0,0 +1,23 @@
+-- =============================================================================
+-- 043: space_members UPDATE — add WITH CHECK (defense-in-depth)
+-- =============================================================================
+-- members_update had only a USING clause: a privileged caller could mutate a
+-- member row into a space where they hold no role (cross-space move) because
+-- the post-image was never re-checked. Add a WITH CHECK mirroring the USING
+-- so the resulting row must still satisfy the same predicate. (Self column
+-- escalation -- space_id/role/status -- is separately blocked by the
+-- prevent_member_self_role_change trigger; see scripts/044.)
+--
+-- Idempotent: DROP POLICY IF EXISTS then CREATE.
+-- =============================================================================
+
+DROP POLICY IF EXISTS members_update ON public.space_members;
+CREATE POLICY members_update ON public.space_members FOR UPDATE
+  USING (
+    user_id = auth.uid()
+    OR public.user_has_role_in_space(auth.uid(), space_id, ARRAY['admin','board','treasurer'])
+  )
+  WITH CHECK (
+    user_id = auth.uid()
+    OR public.user_has_role_in_space(auth.uid(), space_id, ARRAY['admin','board','treasurer'])
+  );