* Change exceeding and nearing limits to account for the 1000th card (instead of 1001)
* Add boundary condition tests for card limit checks
Tests now verify behavior at exactly the limit (1000 cards) and at the
nearing threshold (remaining = 100), covering the off-by-one fix.
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Co-authored-by: Jorge Manrubia <jorge@37signals.com>
Before, we were relying on just changing the cards_count in account, but this
could create problems where the system to calculate the next card number fails due
to the unique constraint.