fix: dark background + emoji favicon for rStack design consistency

Standardize to dark background (#0f172a / slate-900) and add emoji
data URI favicon matching the rStack ecosystem.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/globals.css

@@ -3,15 +3,8 @@
 @tailwind utilities;
 
 :root {
-  --background: #ffffff;
-  --foreground: #171717;
-}
-
-@media (prefers-color-scheme: dark) {
-  :root {
-    --background: #0a0a0a;
-    --foreground: #ededed;
-  }
+  --background: #0f172a;
+  --foreground: #e2e8f0;
 }
 
 body {

app/layout.tsx

@@ -16,6 +16,9 @@ const geistMono = localFont({
 export const metadata: Metadata = {
   title: 'rFunds - Threshold-Based Flow Funding',
   description: 'Design, simulate, and share continuous funding flows with threshold-based mechanisms. Create interconnected funding funnels with overflow routing and outcome tracking.',
+  icons: {
+    icon: "data:image/svg+xml,<svg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 100 100'><text y='.9em' font-size='90'>📊</text></svg>",
+  },
   openGraph: {
     title: 'rFunds - Threshold-Based Flow Funding',
     description: 'Design, simulate, and share continuous funding flows with threshold-based mechanisms.',