feat: add worker distributor and model registry

internal/worker/queries.sql

@@ -2,14 +2,23 @@
 SELECT 1;
 
 -- name: RegisterWorker :exec
-INSERT INTO worker_register (worker_id)
+INSERT INTO worker_register (worker_id, capacity)
 VALUES (
-    $1
+      $1
+    , $2
 );
 
+-- name: GetWorkers :many
+SELECT 
+      worker_id
+    , capacity
+FROM
+    worker_register;
+
 -- name: UpdateWorkerHeartbeat :exec
 UPDATE worker_register
 SET
     heart_beat = now()
 WHERE
     worker_id = $1;
+