Add creator key airdrop so creators can gift keys to a list of wallets at their own cost

[Chucks1093]

Summary

Creators want to reward early community members, run giveaways, or bootstrap a new audience by gifting keys. An airdrop function lets the creator pay the bonding curve price themselves and send keys directly to a list of recipient wallets in a single transaction, without recipients needing to do anything.

Scope

• Add airdrop_keys(creator_id, recipients: Vec<AirdropEntry>) -> AirdropSummary callable only by the creator
  • AirdropEntry { address: Address, amount: u32 }
  • For each recipient: mint amount keys at the current bonding curve price and credit their balance
  • The creator pays the total XLM cost for all keys across all recipients
  • Supply increases by the total airdropped amount, moving the curve normally
  • Creator fee is waived on airdrops (creator is paying themselves); protocol fee applies to the total
  • Maximum 50 recipients per airdrop call
  • Returns AirdropSummary { total_keys, total_cost, recipient_count }
• Emits KeysAirdropped { creator_id, total_keys, total_cost, recipient_count, ledger } event
• Per-wallet cap (if set) is enforced for each recipient — recipients already at the cap are skipped and reported in the summary

Acceptance Criteria

• Each recipient balance increases by their airdropped amount
• Total supply increases by the sum of all airdropped keys
• Creator pays total bonding curve cost for all keys
• Creator fee waived; protocol fee applied to total
• More than 50 recipients reverts with a clear error
• Recipients at their wallet cap are skipped, not reverted
• KeysAirdropped event emitted with correct summary fields
• Non-creator caller reverts with Unauthorized

ETA: 24 hours

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Coordinate on Telegram

[emma008boop]

Hi team! I would love to work on this airdrop feature.

I have carefully read the requirements and the logic for airdrop_keys. I have experience with Rust and Git, and the scope is clear to me. I can handle implementing the bulk minting logic, looping through the recipients, handling the 50-recipient limit, and making sure the creator fee is waived while the protocol fee is correctly applied.