feat: live voice waveform replaces static recording indicator

32-bar waveform visualization that reacts to microphone amplitude in
real-time. MediaRecorder.getMaxAmplitude() polled every 60ms, normalized
to 0-1 range, fed into a scrolling bar chart (new bars enter right, old
shift left). Bars use accent color — louder = taller + more opaque,
quiet = short + muted. Replaces the static "Aufnahme läuft…" text.

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

@@ -50,6 +50,7 @@ import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
 import androidx.compose.ui.draw.clip
 import androidx.compose.ui.draw.scale
+import androidx.compose.ui.geometry.CornerRadius
 import androidx.compose.ui.geometry.Offset
 import androidx.compose.ui.graphics.Brush
 import androidx.compose.ui.graphics.Color
@@ -553,32 +554,51 @@ fun MessageRow(
     }
 }
 
-@Composable
-private fun RecordingIndicator() {
-    val cs = MaterialTheme.colorScheme
-    val transition = rememberInfiniteTransition(label = "rec")
-    val dotAlpha by transition.animateFloat(
-        initialValue = 1f, targetValue = 0.3f,
-        animationSpec = infiniteRepeatable(tween(800, easing = FastOutSlowInEasing), RepeatMode.Reverse),
-        label = "dot",
-    )
+private const val WAVEFORM_BAR_COUNT = 32
 
-    Row(
-        Modifier.fillMaxWidth().heightIn(min = 48.dp),
-        verticalAlignment = Alignment.CenterVertically,
-        horizontalArrangement = Arrangement.Center,
-    ) {
-        Canvas(Modifier.size(10.dp)) {
-            drawCircle(Color(0xFFEF4444).copy(alpha = dotAlpha))
+@Composable
+private fun VoiceWaveform(amplitude: Float) {
+    val accent = LocalKaizenAccent.current
+    val isDark = isSystemInDarkTheme()
+
+    val barHeights = remember { Array(WAVEFORM_BAR_COUNT) { mutableStateOf(0.08f) } }
+
+    LaunchedEffect(amplitude) {
+        // Shift bars left, add new amplitude on the right
+        for (i in 0 until WAVEFORM_BAR_COUNT - 1) {
+            barHeights[i].value = barHeights[i + 1].value
         }
-        Spacer(Modifier.width(10.dp))
-        Text(
-            stringResource(R.string.chat_recording),
-            color = cs.onSurfaceVariant.copy(alpha = 0.70f),
-            fontSize = 15.sp,
-            fontWeight = FontWeight.Medium,
+        barHeights[WAVEFORM_BAR_COUNT - 1].value = (amplitude * 0.85f + 0.08f).coerceIn(0.08f, 0.95f)
+    }
+
+    val barColor = accent.primary.copy(alpha = if (isDark) 0.75f else 0.65f)
+    val mutedColor = accent.primary.copy(alpha = if (isDark) 0.25f else 0.18f)
+
+    Canvas(
+        Modifier
+            .fillMaxWidth()
+            .height(48.dp)
+    ) {
+        val totalWidth = size.width
+        val barWidth = totalWidth / (WAVEFORM_BAR_COUNT * 2f)
+        val gap = barWidth
+        val centerY = size.height / 2f
+        val maxBarHeight = size.height * 0.8f
+
+        for (i in 0 until WAVEFORM_BAR_COUNT) {
+            val h = barHeights[i].value
+            val barH = maxBarHeight * h
+            val x = i * (barWidth + gap) + gap / 2f
+            val color = if (h > 0.12f) barColor else mutedColor
+
+            drawRoundRect(
+                color = color,
+                topLeft = Offset(x, centerY - barH / 2f),
+                size = androidx.compose.ui.geometry.Size(barWidth, barH),
+                cornerRadius = CornerRadius(barWidth / 2f, barWidth / 2f),
             )
         }
+    }
 }
 
 @Composable
@@ -632,6 +652,7 @@ fun ChatInput(
     isStreaming: Boolean = false,
     onStop: () -> Unit = {},
     isRecording: Boolean = false,
+    recordingAmplitude: Float = 0f,
     onMicClick: () -> Unit = {},
     pendingFiles: List<PendingFile> = emptyList(),
     onAddClick: () -> Unit = {},
@@ -658,8 +679,8 @@ fun ChatInput(
     ) {
         Column(Modifier.padding(horizontal = 14.dp, vertical = 14.dp)) {
             if (isRecording) {
-                // Recording state — replaces the text field with a recording indicator
-                RecordingIndicator()
+                // Recording state — live waveform replaces the text field
+                VoiceWaveform(amplitude = recordingAmplitude)
                 Spacer(Modifier.height(10.dp))
                 Row(verticalAlignment = Alignment.CenterVertically) {
                     Spacer(Modifier.weight(1f))

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

@@ -122,6 +122,16 @@ fun ChatScreen(
     var isRecording by remember { mutableStateOf(false) }
     val recorderRef = remember { mutableStateOf<MediaRecorder?>(null) }
     val audioFileRef = remember { mutableStateOf<File?>(null) }
+    var recordingAmplitude by remember { mutableStateOf(0f) }
+
+    LaunchedEffect(isRecording) {
+        if (!isRecording) { recordingAmplitude = 0f; return@LaunchedEffect }
+        while (isRecording) {
+            val amp = try { recorderRef.value?.maxAmplitude ?: 0 } catch (_: Exception) { 0 }
+            recordingAmplitude = (amp / 32768f).coerceIn(0f, 1f)
+            kotlinx.coroutines.delay(60)
+        }
+    }
 
     // TTS playback state
     var playingTtsForId by remember { mutableStateOf<Long?>(null) }
@@ -1055,6 +1065,7 @@ fun ChatScreen(
                                 isStreaming = isStreaming,
                                 onStop = { streamJob?.cancel() },
                                 isRecording = isRecording,
+                                recordingAmplitude = recordingAmplitude,
                                 onMicClick = { toggleRecording() },
                                 pendingFiles = pendingFiles,
                                 onAddClick = { showAttachMenu = !showAttachMenu },