chore(db): add migration and regenerate schema artifacts for per-site probe columns

- Add drizzle/0025_site_post_refresh_probe.sql (ALTER TABLE sites ADD 3 columns)
- Update drizzle/meta/_journal.json (idx=24 entry)
- Regenerate mysql/postgres bootstrap+upgrade SQL and schemaContract.json

drizzle/0025_site_post_refresh_probe.sql

@@ -0,0 +1,3 @@
+ALTER TABLE `sites` ADD `post_refresh_probe_enabled` integer DEFAULT false;
+ALTER TABLE `sites` ADD `post_refresh_probe_model` text DEFAULT '';
+ALTER TABLE `sites` ADD `post_refresh_probe_scope` text DEFAULT 'single';