docs(design): remove SVG, use PNG logo only

SVG icon is no longer in use. public/logo.png (1024x1024 RGBA) is
the single logo asset. DESIGN.md updated accordingly: SVG snippet
removed, wordmark pattern and <head> references updated to PNG.

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

index.html

@@ -0,0 +1,17 @@
+<!doctype html>
+<html lang="en" class="scroll-smooth">
+  <head>
+    <meta charset="UTF-8" />
+    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+    <meta name="description" content="netOrk — self-hosted network orchestration for heterogeneous infrastructure. Discover, monitor, and manage routers, switches, firewalls, and servers from a single UI." />
+    <title>netOrk — Network Orchestration Platform</title>
+    <link rel="icon" href="/logo.png" />
+    <meta property="og:image" content="/logo.png" />
+    <meta property="og:title" content="netOrk — Network Orchestration Platform" />
+    <meta property="og:description" content="Self-hosted network orchestration for heterogeneous infrastructure." />
+  </head>
+  <body>
+    <div id="root"></div>
+    <script type="module" src="/src/main.tsx"></script>
+  </body>
+</html>