fix(lagoon): run deferred:purge and the migrate commands on the app's published database (quick-261106-kt2)

The nightly framework entry deferred:purge failed under serve's worker and
schedule:run with "backpack: duplicate provider for *sql.DB": withDB always
opened and published a second pool. It now reuses the published *gorm.DB and
leaves that pool open; the CLI path (nothing published) is unchanged.

modules/lagoon/commands.go

@@ -483,7 +483,16 @@ func purgeBucket(ctx context.Context, app *backpack.App) (*blob.Bucket, func(),
 	return b, func() { _ = b.Close() }, nil
 }
 
+// withDB runs fn on the app's published database when there is one: an
+// in-process run (the scheduler in serve or schedule:run, through
+// bonfire.Catalog.Call) borrows that pool and leaves it open. Otherwise it
+// opens and publishes a pool for the CLI run and closes it when fn returns.
 func withDB(ctx context.Context, app *backpack.App, fn func(*gorm.DB) error) error {
+	if app != nil {
+		if gdb, ok := app.Lookup[*gorm.DB](); ok && gdb != nil {
+			return fn(gdb)
+		}
+	}
 	sqlDB, gdb, err := OpenFromApp(ctx, app)
 	if err != nil {
 		return err