research_topics::create: bag 8 args into a NewTopic struct (fixes clippy)

The prior signature took (pool, workspace_id, title, description,
outcome_kind, topology_kind, repo_id, created_by) — 8 args, one
over the clippy::too_many_arguments ceiling and blocking CI.

Refactor to a NewTopic<'a> input struct mirroring the NewLoop /
NewSubTopology pattern the codebase already uses. Wizard-side
additions like a repo commit branch land as struct fields
instead of cascading into every call site.

crates/cm-api/tests/topology_jobs.rs

@@ -275,13 +275,15 @@ async fn notify_run_completed_transitions_topic_when_no_siblings_in_flight() {
 
     let topic = research_topics::create(
         &pool,
-        ws.as_uuid(),
-        "Topic",
-        "desc",
-        "spec",
-        "hub_spoke",
-        None,
-        user_id.as_uuid(),
+        research_topics::NewTopic {
+            workspace_id: ws.as_uuid(),
+            title: "Topic",
+            description: "desc",
+            outcome_kind: "spec",
+            topology_kind: "hub_spoke",
+            repo_id: None,
+            created_by: user_id.as_uuid(),
+        },
     )
     .await
     .unwrap();
@@ -326,13 +328,15 @@ async fn notify_run_completed_leaves_topic_processing_when_siblings_in_flight()
 
     let topic = research_topics::create(
         &pool,
-        ws.as_uuid(),
-        "Topic",
-        "desc",
-        "spec",
-        "hub_spoke",
-        None,
-        user_id.as_uuid(),
+        research_topics::NewTopic {
+            workspace_id: ws.as_uuid(),
+            title: "Topic",
+            description: "desc",
+            outcome_kind: "spec",
+            topology_kind: "hub_spoke",
+            repo_id: None,
+            created_by: user_id.as_uuid(),
+        },
     )
     .await
     .unwrap();