feat(branding): new app logo for Tauri + PWA install

Replaced Tauri icon source (icon.png) with new 1024px wheat-stalk
mark on dark background. Regenerated all platform variants via
`tauri icon`: macOS .icns, Windows .ico, Linux PNGs, iOS AppIcon
set, Android adaptive icon foregrounds.

Web: PWA manifest icons (192/512) and apple-touch-icon now use the
new logo. Browser-tab favicon (favicon.svg) unchanged — keeps the
theme-aware wheat mark.

Tauri app: 0.5.1 → 0.5.2.

src-tauri/Cargo.lock

@@ -144,7 +144,7 @@ dependencies = [
 
 [[package]]
 name = "bocken"
-version = "0.5.1"
+version = "0.5.2"
 dependencies = [
  "serde",
  "serde_json",