refactor(search): round xmpDM:duration to the nearest millisecond

Address review feedback: a straight int64 cast truncates toward zero,
so Tika values that produce results like 1234.999... millisecond would
land at 1234 ms instead of 1235 ms. Round before casting so durations
are as accurate as float64 allows.

services/search/pkg/content/tika.go

@@ -267,7 +267,7 @@ func (t Tika) getAudio(meta map[string][]string) *libregraph.Audio {
 		// Tika emits fractional seconds.
 		if f, err := strconv.ParseFloat(v, 64); err == nil {
 			initAudio()
-			audio.SetDuration(int64(f * 1000))
+			audio.SetDuration(int64(math.Round(f * 1000)))
 		}
 	}