Remove "mint" from default features of common crates

[ok300]

Description

This PR removes mint from the default features of cashu, cdk, cdk-sqlite and cdk-redb.

This is because these libraries, in their default state (i.e. as published to crates.io), are typically used in apps integrating the CDK Wallet. Having both mint and wallet features enabled by default can lead to confusion when callers try to resolve imports, for example

use cdk::wallet::MintQuote;
use cdk_common::mint::MintQuote;

especially since some words are ambiguous: mint can mean the act of minting, or the mint as the counterparty.

By removing mint and keeping wallet in the default feature list, this PR removes this possible source of confusion for integrating apps.

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Checklist

• I followed the code style guidelines
• I ran just final-check before committing