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/pubsub_service.rs

@@ -254,7 +254,7 @@ impl PubsubService for PubsubServiceImpl {
                 .get(cx.app_id, name)
                 .await
                 .map_err(|e| PubsubError::Unavailable(e.to_string()))?;
-            if !registered.map(|t| t.external_subscribable).unwrap_or(false) {
+            if !registered.is_some_and(|t| t.external_subscribable) {
                 return Err(PubsubError::SubscriberToken(format!(
                     "pubsub::subscriber_token: topic {name} is not externally subscribable"
                 )));