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/android/app/src/main/kotlin/io/unom/punktfunk/LicensesScreen.kt

@@ -0,0 +1,66 @@
+package io.unom.punktfunk
+
+import androidx.activity.compose.BackHandler
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.rememberScrollState
+import androidx.compose.foundation.verticalScroll
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.remember
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.platform.LocalContext
+import androidx.compose.ui.text.font.FontFamily
+import androidx.compose.ui.unit.dp
+
+/**
+ * Open-source licenses: punktfunk's own license (MIT OR Apache-2.0) plus the third-party software
+ * notices, read from the bundled `THIRD-PARTY-NOTICES.txt` asset (generated by
+ * scripts/gen-third-party-notices.sh). Reached from [SettingsScreen]; Back returns there.
+ */
+@Composable
+fun LicensesScreen(onBack: () -> Unit) {
+    val context = LocalContext.current
+    BackHandler(onBack = onBack)
+
+    val notices = remember {
+        runCatching {
+            context.assets.open("THIRD-PARTY-NOTICES.txt").bufferedReader().use { it.readText() }
+        }.getOrDefault("Third-party notices unavailable.")
+    }
+    val version = remember {
+        runCatching {
+            @Suppress("DEPRECATION")
+            context.packageManager.getPackageInfo(context.packageName, 0).versionName
+        }.getOrNull()
+    }
+
+    Column(
+        modifier = Modifier
+            .fillMaxSize()
+            .verticalScroll(rememberScrollState())
+            .padding(horizontal = 20.dp, vertical = 24.dp),
+        verticalArrangement = Arrangement.spacedBy(16.dp),
+    ) {
+        Text("Open-source licenses", style = MaterialTheme.typography.headlineMedium)
+        if (version != null) {
+            Text(
+                "punktfunk $version",
+                style = MaterialTheme.typography.bodyMedium,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
+        Text(
+            "punktfunk is licensed under MIT OR Apache-2.0, at your option. It uses the open-source " +
+                "components below, each under its own license.",
+            style = MaterialTheme.typography.bodyMedium,
+        )
+        Text(
+            notices,
+            style = MaterialTheme.typography.bodySmall.copy(fontFamily = FontFamily.Monospace),
+        )
+    }
+}

clients/android/app/src/main/kotlin/io/unom/punktfunk/SettingsScreen.kt

@@ -5,6 +5,7 @@ import android.content.pm.PackageManager
 import androidx.activity.compose.BackHandler
 import androidx.activity.compose.rememberLauncherForActivityResult
 import androidx.activity.result.contract.ActivityResultContracts
+import androidx.compose.foundation.clickable
 import androidx.compose.foundation.layout.Arrangement
 import androidx.compose.foundation.layout.Column
 import androidx.compose.foundation.layout.ColumnScope
@@ -44,6 +45,7 @@ import androidx.core.content.ContextCompat
 fun SettingsScreen(initial: Settings, onChange: (Settings) -> Unit, onBack: () -> Unit) {
     var s by remember { mutableStateOf(initial) }
     val context = LocalContext.current
+    var showLicenses by remember { mutableStateOf(false) }
     fun update(next: Settings) {
         s = next
         onChange(next)
@@ -56,6 +58,11 @@ fun SettingsScreen(initial: Settings, onChange: (Settings) -> Unit, onBack: () -
         ActivityResultContracts.RequestPermission(),
     ) { granted -> update(s.copy(micEnabled = granted)) }
 
+    if (showLicenses) {
+        LicensesScreen(onBack = { showLicenses = false })
+        return
+    }
+
     Column(
         modifier = Modifier
             .fillMaxSize()
@@ -143,6 +150,14 @@ fun SettingsScreen(initial: Settings, onChange: (Settings) -> Unit, onBack: () -
                 onCheckedChange = { on -> update(s.copy(statsHudEnabled = on)) },
             )
         }
+
+        SettingsGroup("About") {
+            ClickableRow(
+                title = "Open-source licenses",
+                subtitle = "Third-party notices and credits",
+                onClick = { showLicenses = true },
+            )
+        }
     }
 }
 
@@ -187,6 +202,24 @@ private fun ToggleRow(
     }
 }
 
+/** A title + subtitle on the left; the whole row is clickable (opens a sub-screen). */
+@Composable
+private fun ClickableRow(title: String, subtitle: String, onClick: () -> Unit) {
+    Row(
+        modifier = Modifier.fillMaxWidth().clickable(onClick = onClick),
+        verticalAlignment = Alignment.CenterVertically,
+    ) {
+        Column(Modifier.weight(1f)) {
+            Text(title, style = MaterialTheme.typography.bodyLarge)
+            Text(
+                subtitle,
+                style = MaterialTheme.typography.bodySmall,
+                color = MaterialTheme.colorScheme.onSurfaceVariant,
+            )
+        }
+    }
+}
+
 /** A labelled read-only dropdown over [options] (value → label); calls [onSelect] on a pick. */
 @OptIn(ExperimentalMaterial3Api::class)
 @Composable