[Bug] State queries (eth_getBalance, eth_getTransactionCount, eth_getCode, eth_getStorageAt) treat "earliest" as "latest"

## Type

- [x] Bug
- [ ] Feature
- [ ] Proposal / Discussion

## Summary

State queries (`eth_getBalance`, `eth_getTransactionCount`, `eth_getCode`, `eth_getStorageAt`) treat the `earliest` block tag as `latest`. They derive the gRPC query height from `BlockNumber.Int64()`, which maps every negative sentinel (including `earliest` = -5) to 0, i.e. "use the latest height":

https://github.com/cosmos/evm/blob/469142db41aee479102cf878f8ac2bbe2b0c7a22/rpc/types/block.go#L110-L118

```go
func (bn BlockNumber) Int64() int64 {
if bn < 0 {
return 0
} else if bn == 0 {
return 1
}
return int64(bn)
}
```

Block queries handle the tag correctly because `getHeightByBlockNum` special-cases `EthEarliestBlockNumber` via `status.SyncInfo.EarliestBlockHeight`, so `eth_getBlockByNumber("earliest")` returns block 1 while `eth_getBalance(addr, "earliest")` returns the head state.

## Reproduction (for bugs)

`main` (`469142d`), `./local_node.sh -y`, after sending a few txs from dev0 (`0xc6fe…e101`):

```
eth_getBlockByNumber ["earliest", false] -> number: 0x1
eth_getBalance ["0xc6fe…e101", "0x1"] -> 0x3635c9adc5dea00000 (genesis balance)
eth_getBalance ["0xc6fe…e101", "earliest"] -> 0x3635c9ad2132058000 (== "latest")
eth_getTransactionCount ["0xc6fe…e101", "0x1"] -> 0x0
eth_getTransactionCount ["0xc6fe…e101", "earliest"] -> 0x3 (== "latest")
```

## Impact

Low; spec deviation only (`earliest` must return the genesis/earliest state, as geth does). Fix: resolve `EthEarliestBlockNumber` in the state queries with the same helper the block queries use, and guard `GetTransactionCount`'s future-height check accordingly. Can send a PR if wanted.

## Related

- #1279 (`eth_getProof` has the same tag-handling problem in a different form)

## Checklist

- [x] Linked to a GitHub Issue (or this is the Issue)
- [x] Repro steps included (for bugs)
- [x] Impact described
- [x] I understand minor typo/style doc fixes will not be accepted

Start with rpc/types/block.go and trace the state-query handlers for eth_getBalance, eth_getTransactionCount, eth_getCode, and eth_getStorageAt, comparing them with getHeightByBlockNum and its earliest-block handling. Reproduce the calls against ./local_node.sh -y, then verify that the earliest tag resolves to the earliest state while future-height checks remain correct.

Written by the indexing model from the issue text.