Add per-wallet key holding cap so creators can prevent supply concentration

[Chucks1093]

Summary

Without a per-wallet cap, a single wallet can buy a majority of a creator's keys, dominating the price and locking out genuine fans. Letting creators set a maximum number of keys any single wallet can hold at registration gives communities a fairer distribution from the start.

Scope

• Add optional max_keys_per_wallet: Option<u32> parameter to register_creator
• At the start of buy, check if current_holder_balance + amount > max_keys_per_wallet and revert with WalletCapExceeded if so
• Cap applies to each individual buy; the check is against the post-buy balance
• Peer-to-peer transfers are also subject to the cap — receiving a transfer that would breach the cap reverts with WalletCapExceeded
• Add get_wallet_cap(creator_id) -> Option<u32> view function
• Cap is immutable after registration
• None means no per-wallet limit (current default behavior)

Acceptance Criteria

• Buy that would exceed per-wallet cap reverts with WalletCapExceeded
• Buy up to exactly the cap succeeds
• Transfer that would exceed cap reverts with WalletCapExceeded
• get_wallet_cap returns None for uncapped creators
• No per-wallet limit when None passed at registration
• Cap is immutable — no update function exists

ETA: 24 hours

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Coordinate on Telegram

[shinzoxD]

Hi maintainers, I would like to take this issue if it is available.

I would implement the immutable max_keys_per_wallet creator registration option, enforce the post-buy and transfer receive cap with WalletCapExceeded, add get_wallet_cap, and preserve the current uncapped behavior when the option is None. I would cover exact-cap success, buy-over-cap revert, transfer-over-cap revert, uncapped creators, and immutability/no-update behavior in tests.

I will wait for assignment or GrantFox confirmation before opening a PR.

[codewithzubair07]

i would like to work on this issue