Decode the Items Next Action Indicator (TS 102 223 §8.24)

- tag '18' (TS 101 220: "18 only"): one byte per item, §9.4 coding;
  '00' and reserved values mean "no next action" (decoded to None)
- items[] now carry a per-item next_action; a list whose length differs
  from the item count is preserved raw (spec requires X = item count)
- detail view renders "Item 0xNN: text → COMMAND"; the APDU-list summary
  is unchanged — next actions are detail-only, as requested
- tests: 3 real SET UP MENU samples (local sessions 47/53/57) + a
  length-mismatch tolerance case
- v2.1.2; SW cache simtrace-analyser-v57

frontend/sw.js

@@ -1,4 +1,4 @@
-const CACHE = 'simtrace-analyser-v56';
+const CACHE = 'simtrace-analyser-v57';
 
 const PRECACHE = [
     'index.html',