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/executor-core/tests/sdk_subscriber_token.rs

@@ -197,7 +197,7 @@ async fn unit_ttl_uses_default() {
 async fn empty_topics_throws() {
     run_err(
         make_engine(),
-        r#"pubsub::subscriber_token([], 60)"#,
+        r"pubsub::subscriber_token([], 60)",
         request(AppId::new(), true),
     )
     .await;