Mobile remote: per-track trim (in/out) + waveform + times + scrub/seek + gap

- Queue cards expand to a detail panel with the waveform, elapsed/total/remaining
  times, draggable in/out handles, scrub-to-seek and a 'pausa dopo' gap.
- /api/peaks now also returns exact duration (samples/8000) so non-playing tracks
  have correct times/trim without relying on the output media probe.
- Service worker switched to network-first (+v2) so UI updates aren't masked by
  a stale cache; output.js probeDurations hardened (load()+timeout fallback).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server.js

@@ -103,8 +103,10 @@ app.get('/api/peaks', (req, res) => {
         peaks[b] = m; if (m > top) top = m;
       }
       for (let b = 0; b < buckets; b++) peaks[b] = Math.min(1, peaks[b] / top);
-      peaksCache.set(key, peaks);
-      res.json(peaks);
+      // Exact duration from the decoded mono 8 kHz stream: samples / 8000.
+      const out = { peaks, duration: n / 8000 };
+      peaksCache.set(key, out);
+      res.json(out);
     });
 });