Replace the inline contribution UI (label, input row, presets, guidance)
with the shared ContributionAmountField component, locking cadence and
suppressing its built-in summary (account.vue has its own change hint).
Fix three computeds that double-applied the cadence conversion now that
Member.contributionAmount is stored in cadence-unit (post-Task 7):
contributionChangeHint, currentContributionLabel, and nextChargeAmount
no longer multiply annual amounts by 12.
Convert form.contributionAmount to a monthly-equivalent before the
payment-setup redirect — that page is monthly-only and would otherwise
attempt an annual-sized monthly charge for annual members.
Drop the now-unused guidanceLabel computed, the CONTRIBUTION_PRESETS and
getGuidanceLabel imports, and the dead contribution-* CSS rules.
Jennie Robinson Faber
ad63a37a05