JSV constant: 12 -> 13 (was left behind; stale-cache detection depends on it)

static/app.js

@@ -1,5 +1,5 @@
 // app.js — ani-web frontend: search -> detail -> play, vanilla JS + hls.js
-const JSV = 12;  // bump with every app.js change; play-probe reports it so a
+const JSV = 13;  // bump with every app.js change; play-probe reports it so a
                  // stale-cache phone is detectable server-side
 // BASE = this page's directory, so the app works at / or behind a
 // prefixing reverse proxy (e.g. https://host/ani/)