fix: TTS read-aloud downloads audio via OkHttp before playing

MediaPlayer.setDataSource(url) with HTTPS URLs can silently fail due to
certificate issues, redirect handling, or listener race conditions (listeners
were set after prepareAsync). Fix: download the WAV file via OkHttp (same
client as all other network calls) to a temp file, set listeners before
prepareAsync, play from local path. Temp file cleaned up on completion/error.

app/src/main/java/dev/kaizen/app/chat/ChatScreen.kt

@@ -370,28 +370,44 @@ fun ChatScreen(
     }
 
     fun playTtsUrl(url: String, messageId: Long) {
+        scope.launch {
             try {
+                val tmpFile = kotlinx.coroutines.withContext(kotlinx.coroutines.Dispatchers.IO) {
+                    val req = okhttp3.Request.Builder().url(url).build()
+                    KaizenApi.imageClient.newCall(req).execute().use { resp ->
+                        if (!resp.isSuccessful) return@withContext null
+                        val bytes = resp.body!!.bytes()
+                        java.io.File.createTempFile("tts_", ".wav", context.cacheDir).also { it.writeBytes(bytes) }
+                    }
+                }
+                if (tmpFile == null) {
+                    playingTtsForId = null
+                    return@launch
+                }
                 val player = MediaPlayer().apply {
-                setDataSource(url)
-                prepareAsync()
                     setOnPreparedListener { start() }
                     setOnCompletionListener {
                         release()
                         ttsPlayerRef.value = null
                         playingTtsForId = null
+                        tmpFile.delete()
                     }
                     setOnErrorListener { _, _, _ ->
                         release()
                         ttsPlayerRef.value = null
                         playingTtsForId = null
+                        tmpFile.delete()
                         true
                     }
+                    setDataSource(tmpFile.absolutePath)
+                    prepareAsync()
                 }
                 ttsPlayerRef.value = player
             } catch (_: Exception) {
                 playingTtsForId = null
             }
         }
+    }
 
     fun readAloud(content: String, messageId: Long, wireId: String) {
         val cfg = session.config ?: return