fix(#69): replace mipmap launcher icon with proper notification vector drawable (#95)

Notification smallIcon must use a simple mono vector drawable, not a
launcher mipmap. Launcher icons render broken in the status bar on
many devices.

- Added app/src/main/res/drawable/ic_notification.xml (simple info icon)
- Updated both showReplyNotification and buildForegroundNotification to
  reference R.drawable.ic_notification instead of R.mipmap.ic_launcher

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/main/java/com/m57/hermescontrol/notification/ChatNotificationService.kt

@@ -92,7 +92,7 @@ class ChatNotificationService : Service() {
         val notification =
             NotificationCompat
                 .Builder(this, CHANNEL_ID)
-                .setSmallIcon(R.mipmap.ic_launcher)
+                .setSmallIcon(R.drawable.ic_notification)
                 .setContentTitle("Hermes")
                 .setContentText(text)
                 .setStyle(NotificationCompat.BigTextStyle().bigText(text))
@@ -116,7 +116,7 @@ class ChatNotificationService : Service() {
     private fun buildForegroundNotification(text: String): Notification =
         NotificationCompat
             .Builder(this, CHANNEL_ID)
-            .setSmallIcon(R.mipmap.ic_launcher)
+            .setSmallIcon(R.drawable.ic_notification)
             .setContentTitle("Hermes")
             .setContentText(text)
             .setPriority(NotificationCompat.PRIORITY_LOW)