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/topic_repo.rs

@@ -195,7 +195,7 @@ impl TopicRepo for PostgresTopicRepo {
         .bind(app_id.into_inner())
         .bind(name)
         .bind(external_subscribable)
-        .bind(auth_mode.map(|m| m.as_str()))
+        .bind(auth_mode.map(TopicAuthMode::as_str))
         .fetch_optional(&self.pool)
         .await?;
         row.map(TopicRow::into_topic).transpose()