fix: #3615260 An order's charged amount ignores the line quantity, so a two-ticket line is charged as one

Fixes the charged amount ignoring the line quantity.

• transactionPolicies() now pairs each line's policy with the units that line holds, so no summation site can lose it.
• PaymentPolicy::amountDueNow() takes the quantity as a required argument and multiplies the collected price slice by it. Required rather than defaulting to one unit, because a caller silently omitting it is how this happened.
• The yoyaku_ui bookings table column now shows the line total it was already documented as showing.
• The guarantee and the no-show fee are deliberately untouched, and a characterization test pins that, so [#3615262] changing it later is visible.

Tests: testTransactionAmountDueCountsEveryUnit was seen to fail against unfixed code (returned the unit figure where 40.00 is owed) and passes with the fix. testTransactionAmountDueAddsUpEveryLine covers two lines of several units each.