test(e2e): re-confirm contest poll exists immediately before voting in TC-090

Add a second `wait_for_dpns_contest` call (step 2c) between the initial
"contest created" precheck and the actual `VoteOnDPNSNames` dispatch.
Belt-and-suspenders against poll cleanup between DPNS registration and
voting — e.g. on testnets with short voting windows, or if an earlier
vote already resolved the contest while the test was still setting up.

The first precheck (step 2b) stays on a 30 s budget; the new step 2c
uses a 5 s budget since it's a single query — enough to confirm the
poll is still live without adding meaningful runtime to the happy path.

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

Author: lklimek

tests/backend-e2e/masternode_identity_tasks.rs

@@ -499,6 +499,20 @@ async fn tc_090_vote_with_mn_voter() {
     )
     .await;
 
+    // Step 2c: Re-confirm the contest is still live immediately before voting.
+    // Step 2b proves the poll was ever created; this second, short check
+    // (single query, 5 s cap) catches poll cleanup between registration and
+    // voting — e.g. on testnets with short voting windows, or if an earlier
+    // vote already resolved the contest. Cheap belt-and-suspenders against
+    // opaque vote timeouts.
+    tracing::info!(name = %name, "re-confirming contest is live before voting");
+    wait_for_dpns_contest(
+        &ctx.app_context.sdk(),
+        &name,
+        std::time::Duration::from_secs(5),
+    )
+    .await;
+
     // Step 3: Vote Lock on the contested name using the MN voter identity.
     tracing::info!(name = %name, "voting Lock with MN voter");