Remove embedded music player

The music feature is retired: delete the Media tab, MediaAPI,
MediaPlayerController, PinnedMediaResourceLoader, MediaPanelView, the
media_state control publish, media scope handling in VoiceSession, the
volume setting, and all media tests. App is now Talk + Activity tabs.

Backend media API in hope-voice-api is untouched (still serves the web UI).

Sources/Features/Conversation/ConversationView.swift

@@ -40,15 +40,8 @@ struct ConversationView: View {
             .tabItem { Label("Talk", systemImage: "waveform") }
             .tag(0)
 
-            NavigationStack {
-                MediaPanelView(playerController: session.mediaController, settings: settings)
-                    .toolbar { settingsLink }
-            }
-            .tabItem { Label("Music", systemImage: "music.note") }
-            .tag(1)
-
             ActivityTab(taskStore: session.taskStore, settings: settings, session: session)
-                .tag(2)
+                .tag(1)
         }
         .id(sessionID)
         .tint(HopeStyle.tint)
@@ -79,9 +72,7 @@ struct ConversationView: View {
             // Coalesce rapid Apply actions; construct from the captured URL.
             while let next = pendingServerURL {
                 pendingServerURL = nil
-                guard next != activeServerURL else { continue }
                 await session.disconnect()
-                session.mediaController.resetScope()
                 activeServerURL = next
                 session = Self.makeSession(next, settings: settings)
                 sessionID = UUID()
@@ -157,13 +148,12 @@ private struct ConversationContent: View {
                     Text("A little help.\nA good conversation.")
                         .font(.largeTitle.weight(.semibold))
                         .fixedSize(horizontal: false, vertical: true)
-                    Text("Talk things through, find something out, or put on a favorite song.")
+                    Text("Talk things through, find something out, or get something done.")
                         .font(.body).foregroundStyle(.secondary)
                 }
                 VStack(alignment: .leading, spacing: 16) {
                     Label("Think out loud", systemImage: "bubble.left.and.bubble.right")
                     Label("Find an answer", systemImage: "sparkle.magnifyingglass")
-                    Label("Make time for music", systemImage: "music.note")
                 }
                 .font(.subheadline).foregroundStyle(.secondary)
             }