chore: reorganize icons for environment-specific deployment

Move environment-specific icons into dedicated directories (icons/develop, icons/test, icons/production) and update release scripts to copy the appropriate icon set (favicon.ico, Icon-192.png, Icon-512.png) into public/ for each target environment. Update manifest.json to reference the new /images/icons/ path.

public/manifest.json

@@ -11,13 +11,13 @@
   "lang": "en",
   "icons": [
     {
-      "src": "/images/splash/Icon-192.png",
+      "src": "/images/icons/Icon-192.png",
       "sizes": "192x192",
       "type": "image/png",
       "purpose": "any"
     },
     {
-      "src": "/images/splash/Icon-512.png",
+      "src": "/images/icons/Icon-512.png",
       "sizes": "512x512",
       "type": "image/png",
       "purpose": "any"