chore: fix compiler warnings in quicproquo-core

Remove unused LeafNodeIndex import and dead StoreCrypto struct.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

crates/quicproquo-core/src/keystore.rs

@@ -5,11 +5,7 @@ use std::{
     sync::RwLock,
 };
 
-use openmls_rust_crypto::RustCrypto;
-use openmls_traits::{
-    key_store::{MlsEntity, OpenMlsKeyStore},
-    OpenMlsCryptoProvider,
-};
+use openmls_traits::key_store::{MlsEntity, OpenMlsKeyStore};
 
 /// A disk-backed key store implementing `OpenMlsKeyStore`.
 ///
@@ -106,42 +102,3 @@ impl OpenMlsKeyStore for DiskKeyStore {
     }
 }
 
-/// Crypto provider that couples RustCrypto with a disk-backed key store.
-#[derive(Debug)]
-pub struct StoreCrypto {
-    crypto: RustCrypto,
-    key_store: DiskKeyStore,
-}
-
-impl StoreCrypto {
-    pub fn new(key_store: DiskKeyStore) -> Self {
-        Self {
-            crypto: RustCrypto::default(),
-            key_store,
-        }
-    }
-}
-
-impl Default for StoreCrypto {
-    fn default() -> Self {
-        Self::new(DiskKeyStore::ephemeral())
-    }
-}
-
-impl OpenMlsCryptoProvider for StoreCrypto {
-    type CryptoProvider = RustCrypto;
-    type RandProvider = RustCrypto;
-    type KeyStoreProvider = DiskKeyStore;
-
-    fn crypto(&self) -> &Self::CryptoProvider {
-        &self.crypto
-    }
-
-    fn rand(&self) -> &Self::RandProvider {
-        &self.crypto
-    }
-
-    fn key_store(&self) -> &Self::KeyStoreProvider {
-        &self.key_store
-    }
-}