Use fixed size array for asset_id

[PaulLaux]

• A fixed size for asset_id
• Removed RTL chars to avoid confusing the text editor.
• Minor spacing fixes

[Copilot]

Pull Request Overview

This PR enforces a fixed 65-byte format for the asset_id by updating the asset_digest function signature and modifying the asset ID encoding in the derive method.

• Change asset_digest parameter type from Vec to [u8; 65].
• Update the construction of the asset ID in derive() to use a fixed-size array.
• Adjust in-code comments to align with the new fixed-size asset representation.

[ConstanceBeguier]

Replace asset_id with AssetBase in the following comments

impl AssetBase {
    /// Deserialize the asset_id from a byte array.
    pub fn from_bytes(bytes: &[u8; 32]) -> CtOption<Self> {
        pallas::Point::from_bytes(bytes).map(AssetBase)
    }
    /// Serialize the asset_id to its canonical byte representation.
    pub fn to_bytes(self) -> [u8; 32] {
        self.0.to_bytes()
    }
    ```

[ConstanceBeguier]

Approved after taking previous minor comments into account.