feat: verification in accept link

Author: ANISH-SR

smartcontract/programs/doublezero-serviceability/src/processors/link/accept.rs

@@ -75,6 +75,11 @@ pub fn process_accept_link(
         return Err(DoubleZeroError::InvalidStatus.into());
     }
 
+    // Validate that the stored side_z_pk matches the provided side_z_account
+    if link.side_z_pk != *side_z_account.key {
+        return Err(DoubleZeroError::InvalidAccountOwner.into());
+    }
+
     // Validate Side Z Device
     let side_z_dev = Device::try_from(side_z_account)?;
     if side_z_dev.contributor_pk != *contributor_account.key {