feat: carry Kii v0.6 patches onto v0.7.3

[mattkii]

Description

Review the five Kii patches carried from the v0.6 fork onto cosmos/evm v0.7.3. This pull request targets base/v0.7.3 (c3ae9067), so the diff is those commits only.

The other v0.6 fork fixes (StateDB overflow and underflow guards, commit atomicity, locked-balance snapshot, gasCap, precompile gas, ERC20 and ICS-20 acks, Ledger coin type) are already in v0.7.3.

Brought from the v0.6 fork:

• Refund unused EVM gas in the denom that was actually paid (ContextPaidFeesKey, capped by the amount paid).
• Reject contract creation unless the account is empty or a plain BaseAccount (IsBaseAccountOrEmpty).
• Skip non-20-byte accounts when mirroring balances, and reject a non-20-byte distribution withdraw address.
• Use the sign-doc chain id for EIP-712 when it parses as a uint64.
• Treat an already-known EVM tx as CheckTx success, and return ErrAlreadyKnown from SendRawTransaction.

After this is approved, tag the merged commit as the new fork line. main stays on the v0.6 fork (v0.6.2-fork.2) until then.

Kiichain will follow the v0.6.x → v0.7.0 migration guide on feat/evm-v0.7.3: bump Go 1.25, cosmos-sdk v0.54, cometbft v0.39, ibc-go v11, and geth 1.17; replace ExperimentalEVMMempool with Krakatoa; recopy the fee-abstraction EVM ante so it still sets ContextPaidFeesKey; drop x/precisebank; leave BlockSTM off for the first cut.

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I have...

• tackled an existing issue or discussed with a team member
• left instructions on how to review the changes
• targeted base/v0.7.3 (v0.7.3). main is still the v0.6 fork and is not the review base

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