fix: add statement-breakpoint separators to multi-statement migrations

Drizzle's better-sqlite3 migrator splits on '--> statement-breakpoint'.
Without it, the entire file is passed to db.prepare() as a single
statement, which better-sqlite3 rejects with 'more than one statement'.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

drizzle/0005_remove_static_response.sql

@@ -1,4 +1,6 @@
 -- Remove static response feature columns from proxy_hosts
 ALTER TABLE `proxy_hosts` DROP COLUMN `response_mode`;
+--> statement-breakpoint
 ALTER TABLE `proxy_hosts` DROP COLUMN `static_status_code`;
+--> statement-breakpoint
 ALTER TABLE `proxy_hosts` DROP COLUMN `static_response_body`;