use strict verification for ed25519

This enables all the signature malleability checks (including one that
is not RFC8032 compliant but are still likely important for Veilid.)

For details on the additional check, see
https://docs.rs/ed25519-dalek/2.0.0/ed25519_dalek/struct.VerifyingKey.html#method.verify_strict

veilid-core/src/crypto/vld0/mod.rs

@@ -225,7 +225,7 @@ impl CryptoSystem for CryptoSystemVLD0 {
         let mut dig = Blake3Digest512::new();
         dig.update(data);
 
-        pk.verify_prehashed(dig, None, &sig)
+        pk.verify_prehashed_strict(dig, None, &sig)
             .map_err(|e| VeilidAPIError::parse_error("Verification failed", e))?;
         Ok(())
     }