feat(key-wallet): expose instant_send_locks accessor on ManagedWalletInfo (#712)

Adds a read-only `instant_send_locks()` getter so external diagnostic
surfaces (e.g. the iOS memory explorer) can list the txids that have
received an IS-lock without bypassing the `pub(crate)` mutation
boundary on the field.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: QuantumExplorer

key-wallet/src/wallet/managed_wallet_info/mod.rs

@@ -126,6 +126,17 @@ impl ManagedWalletInfo {
     pub fn increment_transactions(&mut self) {
         self.metadata.total_transactions += 1;
     }
+
+    /// Read-only access to the InstantSend lock txid set.
+    ///
+    /// Exposes `instant_send_locks` (a `pub(crate)` field marked
+    /// `serde(skip)`) so external diagnostic surfaces (e.g. the iOS
+    /// memory explorer) can list the txids that have received an
+    /// IS-lock without bypassing the encapsulation that keeps mutation
+    /// inside this crate.
+    pub fn instant_send_locks(&self) -> &HashSet<Txid> {
+        &self.instant_send_locks
+    }
 }
 
 /// Re-export types from account module for convenience