Add owner-only room backup snapshots and audited exports

drizzle/0017_admin_room_backups.sql

@@ -0,0 +1,15 @@
+CREATE TABLE `admin_room_backups` (
+  `operation_id` text PRIMARY KEY NOT NULL,
+  `actor_admin_id` text NOT NULL,
+  `room_code` text NOT NULL,
+  `request_hash` text NOT NULL,
+  `room_version` integer NOT NULL,
+  `created_at` integer NOT NULL,
+  `size_bytes` integer NOT NULL,
+  `digest` text NOT NULL,
+  `payload` text NOT NULL,
+  `reason` text NOT NULL,
+  CONSTRAINT `admin_room_backups_size` CHECK (`size_bytes` BETWEEN 1 AND 1800000 AND `size_bytes` = length(CAST(`payload` AS BLOB)))
+);
+--> statement-breakpoint
+CREATE INDEX `admin_room_backups_room` ON `admin_room_backups` (`room_code`,`created_at`);