Play sound-pack notifications for client actions

Adds TeamSpeak-format sound packs: a folder of waves plus a settings.ini
mapping actions to play()/say() entries, with ${clientType} and friends
resolved per event. Packs are found in the client's own sound folder, an
installed TS3 client and a folder of the user's choosing, so the official
packs work unchanged.

Each action can be switched off or marked important; important actions are
the only ones still played while the speakers are muted, as in TS3. The new
Notifications options page lists them by category, greys out what the active
pack has no sound for, and previews on double-click.

Sounds are decoded, resampled and mixed onto a single playback line that is
only open while something plays, so overlapping events never fight over the
device.

Fires the events from the protocol layer, following TeamSpeak's own
distinctions: reason ids separate switched/moved/kicked/banned/timed out,
and visibility decides appears/disappears/stays.

Also fixes a ts3j trap in the process: a field an event never carried reads
back as an empty string, so the existing "e.get(x) != null" checks were
always true. That made a partial clientupdate (someone muting) announce a
stopped recording, and it let a nickname-only update reset another client's
mute/away flags and talk power, or a channel edit blank the channel name.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

ts3-client/swing/src/main/java/com/ts3client/ui/ServerTab.java

@@ -8,6 +8,7 @@ import com.ts3client.net.ChannelNode;
 import com.ts3client.net.ClientEntry;
 import com.ts3client.net.ConnectionListener;
 import com.ts3client.net.TeamspeakConnection;
+import com.ts3client.sound.SoundNotifier;
 import com.ts3client.text.TsLink;
 
 import javax.swing.JComponent;
@@ -52,11 +53,12 @@ final class ServerTab implements ConnectionListener, ServerTreePanel.Actions {
 
     private Object currentSelection;
 
-    ServerTab(MainFrame host, Settings settings, IdentityStore identities, AudioBackend audio) {
+    ServerTab(MainFrame host, Settings settings, IdentityStore identities, AudioBackend audio,
+              SoundNotifier sounds) {
         this.host = host;
         this.settings = settings;
         this.identities = identities;
-        this.conn = new TeamspeakConnection(settings, audio, this);
+        this.conn = new TeamspeakConnection(settings, audio, this, sounds);
         this.groupIcons = new GroupIcons(conn.getIcons());
         this.treePanel = new ServerTreePanel(conn.getModel(), groupIcons, this);
         this.chatPanel = new ChatPanel();