fix(pumpswap): align remaining accounts with official SDK for buyback

- Append pool-v2 in buy/sell remaining accounts only when pool coin_creator
  is not default, matching @pump-fun/pump-swap-sdk. Always appending pool-v2
  shifted buyback pubkey/ATA and caused BuybackFeeRecipientNotAuthorized (6053).

- Add coin_creator to PumpSwapParams (filled from decoded Pool / from_trade).
  Update pumpswap_trading example to pass pool_data.coin_creator.

- Document buyback fee recipient constants against GlobalConfig.buyback_fee_recipients.

- Extend PumpSwap quote math to include cashback_fee_basis_points in creator-side fees.

Co-authored-by: Cursor <cursoragent@cursor.com>

examples/pumpswap_trading/src/main.rs

@@ -162,7 +162,9 @@ async fn pumpswap_trade_with_grpc_buy_event(trade_info: PumpSwapBuyEvent) -> Any
         trade_info.base_token_program,
         trade_info.quote_token_program,
         trade_info.protocol_fee_recipient,
+        pool_data.coin_creator,
         pool_data.is_cashback_coin,
+        trade_info.cashback_fee_basis_points,
     );
     let mint = if trade_info.base_mint == sol_trade_sdk::constants::USDC_TOKEN_ACCOUNT
         || trade_info.base_mint == sol_trade_sdk::constants::WSOL_TOKEN_ACCOUNT
@@ -191,7 +193,9 @@ async fn pumpswap_trade_with_grpc_sell_event(trade_info: PumpSwapSellEvent) -> A
         trade_info.base_token_program,
         trade_info.quote_token_program,
         trade_info.protocol_fee_recipient,
+        pool_data.coin_creator,
         pool_data.is_cashback_coin,
+        trade_info.cashback_fee_basis_points,
     );
     let mint = if trade_info.base_mint == sol_trade_sdk::constants::USDC_TOKEN_ACCOUNT
         || trade_info.base_mint == sol_trade_sdk::constants::WSOL_TOKEN_ACCOUNT