fix(eq): re-apply the equalizer after an audio-focus interruption

The equalizer stopped applying after another app interrupted audio (e.g. a
navigation app's voice prompt): play a station with EQ working, let the
prompt speak, resume -- the audio sounds flat until the station is
re-tapped.

debeReaplicarEcualizador only re-attaches the equalizer when the native
player session id actually changes. A short transient interruption keeps
the SAME session (no id rotation), so that trigger never fires, while
Android's AudioEffect framework can let a higher-priority client silently
disable this app's effect instance in the meantime.

Add reaplicarEcualizador() to ObjetivoAudioInterrumpible, implemented as a
thin delegate to the existing _activarEcualizador() (already the correct
idempotent setEnabled + re-push-gains path). ServicioAudioSession calls it
on resume-from-pause (after reanudar()) and on un-duck (after
setAtenuado(false)) -- additive to the existing session-id trigger, not a
replacement. The method takes no argument, so it can only re-assert
whatever enabled/disabled state the handler already holds -- an
interruption cycle with the equalizer OFF stays OFF.

test/servicios/servicio_audio_session_test.dart

@@ -33,6 +33,13 @@ class _ObjetivoFake implements ObjetivoAudioInterrumpible {
   Future<void> setAtenuado(bool atenuado) async {
     atenuaciones.add(atenuado);
   }
+
+  int reaplicaciones = 0;
+
+  @override
+  Future<void> reaplicarEcualizador() async {
+    reaplicaciones++;
+  }
 }
 
 /// S3-R1: audio-session interruptions (phone call, transient loss, duck) and