feat: re-order lists

internal/database/migrations/000006_add_list_position.up.sql

@@ -0,0 +1,20 @@
+BEGIN;
+
+ALTER TABLE IF EXISTS list_users
+    ADD COLUMN IF NOT EXISTS position NOT NULL DEFAULT 0;
+
+CREATE INDEX IF NOT EXISTS idx_list_users_user_id_position ON list_users (user_id, position);
+
+UPDATE list_users lu
+    SET position = r.rn - 1
+FROM (SELECT list_id,
+             user_id,
+             row_number() OVER (
+                 PARTITION BY user_id
+                 ORDER BY created_at, list_id
+                 ) AS rn
+      FROM list_users) r
+WHERE lu.list_id = r.list_id
+  AND lu.user_id = r.user_id;
+
+COMMIT;