Reverts the CreateWorkspace-outside-transaction change from the previous commit.
That move was based on a mis-framed concern: forgetPlanFeatureCache() uses
Pennant's default 'database' store (no config/pennant.php), so it's a DB write,
not an external cache call — safe inside a DB transaction. Moving CreateWorkspace
out introduced two failure-path regressions: a stranded half-registered account
(user committed but not logged in, blocked from retrying by unique:users) and an
orphan workspace inflating the Stripe quantity. Back inside the transaction the
whole signup is atomic again.
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