Tag connect requests as v9 + clippy unblocker

- nym-ip-packet-client/connect.rs: current::request::IpPacketRequest::new_connect_request
  leaves protocol.version=8 (v9 re-exports v8 types). Use the v9 wrapper so
  the client honestly advertises v9 to the IPR; pairs with the v9-accepts-v8
  reply compat in nym-ip-packet-requests for older gateways.
- nym_offline_compact_ecash/proofs: pre-existing manual_saturating_arithmetic
  lint surfaced after toolchain bump; replace checked_sub().unwrap_or_default()
  with saturating_sub. Behaviorally identical, unblocks workspace clippy
  -D warnings (caught by `cargo clippy --workspace --all-targets`).

common/nym_offline_compact_ecash/src/proofs/mod.rs

@@ -31,9 +31,7 @@ where
     // instead we could maybe use the `from_bytes` variant and adding some suffix
     // when computing the digest until we produce a valid scalar.
     let mut bytes = [0u8; 64];
-    let pad_size = 64usize
-        .checked_sub(D::OutputSize::to_usize())
-        .unwrap_or_default();
+    let pad_size = 64usize.saturating_sub(D::OutputSize::to_usize());
 
     bytes[pad_size..].copy_from_slice(&digest);
 

nym-ip-packet-client/src/connect.rs

@@ -80,7 +80,7 @@ impl IprClientConnect {
     }
 
     async fn send_connect_request(&self, ip_packet_router_address: Recipient) -> Result<u64> {
-        let (request, request_id) = IpPacketRequest::new_connect_request(None);
+        let (request, request_id) = nym_ip_packet_requests::v9::new_connect_request(None);
 
         // We use 20 surbs for the connect request because typically the IPR is configured to have
         // a min threshold of 10 surbs that it reserves for itself to request additional surbs.