0.36.1: app logo as browser-tab favicon

Add frontend/public/favicon.svg (the TopNav LogoMark glyph as a
standalone SVG) and link it from index.html so the StackPilot logo
shows in browser tabs. Vite copies public/ into dist on build.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/package.json

@@ -1,7 +1,7 @@
 {
   "name": "stackpilot-frontend",
   "private": true,
-  "version": "0.36.0",
+  "version": "0.36.1",
   "type": "module",
   "scripts": {
     "dev": "vite",