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/src/routes/research.rs

@@ -368,13 +368,15 @@ pub async fn create_topic(
 
     let id = cm_db::repo::research_topics::create(
         &state.pool,
-        user.workspace_id.as_uuid(),
-        body.title.trim(),
-        body.description.trim(),
-        &body.outcome_kind,
-        topology_kind,
-        repo_id,
-        user.user_id.as_uuid(),
+        cm_db::repo::research_topics::NewTopic {
+            workspace_id: user.workspace_id.as_uuid(),
+            title: body.title.trim(),
+            description: body.description.trim(),
+            outcome_kind: &body.outcome_kind,
+            topology_kind,
+            repo_id,
+            created_by: user.user_id.as_uuid(),
+        },
     )
     .await?;