feat(clients): in-app OSS / third-party-license screens

Surface THIRD-PARTY-NOTICES.txt in every GUI client (the desktop packages already
ship it as a file; this adds the on-glass screen):

- Linux: Preferences -> About -> Third-party licenses (adw::AboutDialog with the app
  license + Legal sections; include_str! the root notices).
- Apple: macOS About tab / iOS+tvOS Acknowledgements link; notices bundled as
  PunktfunkKit SPM resources, read via Bundle.module (the Xcode app links the SPM
  product, so they ride along - no .pbxproj edit).
- Android: Settings -> About -> Open-source licenses (reads the bundled asset).
- (Windows landed earlier in d1d2ca2: Settings -> About -> Third-party licenses.)

gen-third-party-notices.sh now copies the generated file into the Apple Resources/
and Android assets/ trees so the in-tree copies never drift.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

clients/apple/Sources/PunktfunkClient/SettingsView.swift

@@ -98,6 +98,9 @@ struct SettingsView: View {
             }
             .formStyle(.grouped)
             .tabItem { Label("Advanced", systemImage: "slider.horizontal.3") }
+
+            AcknowledgementsView()
+                .tabItem { Label("About", systemImage: "info.circle") }
         }
         .frame(width: 480, height: 460)
     }
@@ -115,6 +118,9 @@ struct SettingsView: View {
             statisticsSection
             experimentalSection
             controllersSection
+            Section {
+                NavigationLink("Acknowledgements") { AcknowledgementsView() }
+            }
         }
         .formStyle(.grouped)
         .onAppear {
@@ -217,6 +223,8 @@ struct SettingsView: View {
                     .foregroundStyle(.secondary)
                     .multilineTextAlignment(.center)
                     .padding(.top, 8)
+                NavigationLink("Acknowledgements") { AcknowledgementsView() }
+                    .padding(.top, 8)
             }
             .frame(maxWidth: 1000)
             .frame(maxWidth: .infinity)