feat: add worker distributor and model registry

internal/modelschedule/queries.sql

@@ -0,0 +1,18 @@
+-- name: Ping :one
+SELECT 1;
+
+-- name: GetLast :one
+SELECT last_run
+FROM
+    model_schedules
+WHERE
+    model_name = $1
+LIMIT 1;
+
+-- name: UpsertModel :exec
+INSERT INTO model_schedules (model_name, last_run)
+VALUES ($1, $2)
+ON CONFLICT (model_name)
+DO UPDATE SET
+last_run = excluded.last_run;
+