feat(app): app icon and macOS bundle config

The dock showed a black square because tauri.conf.json had no bundle.icon
block and icons/ held only tiny placeholders with no .icns. Add an SVG
source logo (terminal prompt + split workspace panes), generate the full
icon set via `tauri icon` (icon.icns/.ico + all PNG/iOS/Android sizes), and
wire bundle.icon so the daemon embeds and macOS renders it.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/src-tauri/icons/android/mipmap-anydpi-v26/ic_launcher.xml

@@ -0,0 +1,5 @@
+<?xml version="1.0" encoding="utf-8"?>
+<adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
+  <foreground android:drawable="@mipmap/ic_launcher_foreground"/>
+  <background android:drawable="@color/ic_launcher_background"/>
+</adaptive-icon>

app/src-tauri/icons/android/values/ic_launcher_background.xml

@@ -0,0 +1,4 @@
+<?xml version="1.0" encoding="utf-8"?>
+<resources>
+  <color name="ic_launcher_background">#fff</color>
+</resources>