Replace generic cloud-lightning logo with custom network nexus mark

The new icon represents Wild Central's role as a network hub —
a central node radiating connections to services. Updated favicon,
sidebar logo component, theme color, and PWA manifest name.

web/public/manifest.json

@@ -1,6 +1,6 @@
 {
-  "short_name": "Wild Cloud",
-  "name": "Wild Cloud Central",
+  "short_name": "Wild Central",
+  "name": "Wild Central",
   "icons": [
     {
       "src": "favicon.svg",
@@ -10,6 +10,6 @@
   ],
   "start_url": ".",
   "display": "standalone",
-  "theme_color": "#0ea5e9",
+  "theme_color": "#2563eb",
   "background_color": "#ffffff"
 }