fix admin_migrateToGroups (tldraw#7049)

testing this some more in production I noticed that it was not
effectively clearing the cache data for users who aren't signed in and
active. That's because if they aren't connected there's no cache so the
reboot doesn't get called. this fixes that.

### Change type

- [x] `other`

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Deletes the user's R2 snapshot before rebooting in
`admin_migrateToGroups` to properly reset cache for offline users, and
adds more detailed debug logs around migration and reboots.
> 
> - **Sync Worker**
> - **Migration flow**
(`apps/dotcom/sync-worker/src/TLUserDurableObject.ts`):
> - Delete user snapshot
`USER_DO_SNAPSHOTS.delete(getUserDoSnapshotKey(...))` before cache
reboot in `admin_migrateToGroups` to ensure fresh state.
>     - Add debug logs: start, result, and completion of migration.
> - **Reboot logging**
(`apps/dotcom/sync-worker/src/UserDataSyncer.ts`):
> - Expand `reboot` debug message to include `hard` and `delay` flags.
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
65e16b9. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

Author: ds300

apps/dotcom/sync-worker/src/TLUserDurableObject.ts

@@ -565,16 +565,21 @@ export class TLUserDurableObject extends DurableObject<Environment> {
 	async admin_migrateToGroups(userId: string, inviteSecret: string | null = null) {
 		this.userId ??= userId
 
+		this.log.debug('migrating to groups', userId, inviteSecret)
 		// Call the Postgres migration function
 		const result = await sql<{
 			files_migrated: number
 			pinned_files_migrated: number
 			flag_added: boolean
 		}>`SELECT * FROM migrate_user_to_groups(${userId}, ${inviteSecret})`.execute(this.db)
 
-		// Reboot the user's cache to pick up the new data structure
+		this.log.debug('migration result', result.rows[0])
+
+		await this.env.USER_DO_SNAPSHOTS.delete(getUserDoSnapshotKey(this.env, userId))
 		await this.cache?.reboot({ delay: false, source: 'admin', hard: true })
 
+		this.log.debug('migration complete, user rebooted')
+
 		return result.rows[0]
 	}
 

apps/dotcom/sync-worker/src/UserDataSyncer.ts

@@ -262,7 +262,7 @@ export class UserDataSyncer {
 			this.ctx.abort()
 			return
 		}
-		this.log.debug('rebooting', source)
+		this.log.debug('rebooting', source, 'hard:', hard, 'delay:', delay)
 		this.logEvent({ type: 'reboot', id: this.userId })
 		await this.queue.push(async () => {
 			if (delay) {