[Bug]: Invalid type assigned to literals

### Describe the issue:

It appears that IR considers literals as `uint256` or `int256` type, but they should be assigned the smallest possible type instead.

### Code example to reproduce the issue:

```solidity
function test5(uint40 x) external view returns (uint256 res) {
res = x * 50;
}
```

`50` should be `uint8`, but `ir.variable_right.type` returns `uint256`.

### Version:

0.9.2

### Relevant log output:

_No response_

Use the supplied test5 Solidity example to reproduce the reported type on variable_right.type. Trace the IR type-inference path that assigns the literal's type, then verify that 50 is represented with the smallest possible type rather than uint256. Done means the example reports the expected literal type and a regression test covers it.

Written by the indexing model from the issue text.