fix: make byok_enabled non_nullable

Author: tomharmon

supabase/migrations/20250912210821_byok_enabled_non_nullable.sql

@@ -0,0 +1,7 @@
+UPDATE provider_keys
+SET byok_enabled = TRUE
+WHERE byok_enabled IS NULL;
+
+ALTER TABLE IF EXISTS provider_keys
+  ALTER COLUMN byok_enabled SET DEFAULT TRUE,
+  ALTER COLUMN byok_enabled SET NOT NULL;