feat(#2591): add GET /api/build-log/<node_id> {,/raw} query endpoints

The raw-graph wire drops the inline build_log_id; the client fetches a
node's captured output on demand. Two handlers resolve node id -> log-row
id (JobQueue::build_log_id_of, now keyed by the wire u64) then delegate to
the existing get_full / raw handlers: /api/build-log/<node_id> serves the
BuildLogFull JSON ({stdout, stderr} + header), /raw serves text/plain.
404 when the node has no linked log.

hive-c0re/src/job_queue/tests.rs

@@ -896,7 +896,7 @@ fn set_build_log_id_links_running_node() {
     // The log id is fetched by node id (the `GET /api/build-log/<id>` lookup),
     // not carried on the wire — it survives completion in the node runtime.
     assert_eq!(
-        q.build_log_id_of(c.node_id),
+        q.build_log_id_of(c.node_id.get()),
         Some(43),
         "log id survives completion"
     );