chore(v1.1.7): fix clippy --all-targets warnings

Clears the workspace under `clippy --all-targets --all-features
-D warnings`. Four were pre-existing at v1.1.6 HEAD (latent finding,
see HANDBACK): double_must_use on realtime_router, map_unwrap_or in
pubsub_service, redundant_closure in topic_repo, needless_raw_string in
a subscriber-token test. The rest are v1.1.7 nits (needless_borrow +
semicolon in the dead-letter / realtime-migration code).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/manager-core/src/dispatcher.rs

@@ -496,7 +496,7 @@ impl Dispatcher {
         // top of this function, so this fan-out is only reached for
         // non-handler executions.
         if let Some(dl_id) = dl_id {
-            self.fan_out_dead_letter(&row, &resolved, dl_id, &source, attempt, &err, now)
+            self.fan_out_dead_letter(row, resolved, dl_id, &source, attempt, &err, now)
                 .await;
         }