music on hold: play order set in the UI, and shuffle

Owner: the first upload always played first. A class is now an Asterisk playlist in the order
set on Sounds & music (move up/down), new uploads last, with a Shuffle option (sort = random).
moh-test.ts plays both in a real Asterisk and reads the file order from its debug log.

apps/api/src/db/migrations/meta/_journal.json

@@ -36,6 +36,13 @@
       "when": 1792512298128,
       "tag": "0004_system_events",
       "breakpoints": true
+    },
+    {
+      "idx": 5,
+      "version": "7",
+      "when": 1792606712441,
+      "tag": "0005_moh_order",
+      "breakpoints": true
     }
   ]
 }