Seven-day trials and safer export recovery

Eligible accounts can now start one card-required seven-day trial. The trial keeps its credits separate from Free credits, shows the exact end date and next plan, and lets you change the renewal plan, update the card, start the paid plan early, or cancel renewal without losing the remaining trial period.

Failed generation and export attempts now release reserved credits when no result is delivered. Export retries can recover from a failed worker attempt without charging twice, while remote source images are prepared more reliably for PDF and PNG rendering.