talk: use chiron.jpeg as notification icon

Replace generic audio-x-generic icon with chiron.jpeg fetched from S3
into the nix store at build time.

pkgs/talk/default.nix

@@ -2,12 +2,17 @@
   lib,
   stdenv,
   writeShellScriptBin,
+  fetchurl,
   curl,
   python3,
   mpv,
   libnotify,
   busybox,
 }: let
+  icon = fetchurl {
+    url = "https://s3.m3tam3re.com/public/chiron.jpeg";
+    hash = "sha256-LIIR3aqJ5ePsZuvVQxJ70c6yd+L85fLE5uY/fLE5Ypo=";
+  };
   script = writeShellScriptBin "talk" ''
     #!/usr/bin/env bash
     set -euo pipefail
@@ -76,7 +81,7 @@
       exec "$NOTIFY" \
         --action=cancel="⛔ Abbrechen" \
         --urgency=normal \
-        --icon=audio-x-generic \
+        --icon=${icon} \
         "🔊 KI Antwort" \
         "$TEXT" > "$ACTION_FILE" 2>/dev/null
     ) &