Implements #16/#17/#36: Founders/Standard/Pro/Business/Backer catalog, Backer email whitelist, prompt-window + token-period gates, and tokens_in/out on conversation/prompt + subscription usage APIs.
Implements #16/#17/#36: Founders/Standard/Pro/Business/Backer catalog, Backer email whitelist, prompt-window + token-period gates, and tokens_in/out on conversation/prompt + subscription usage APIs.