fix: use BASE_PATH for favicon references in subpath deployments

Hardcoded /favicon.svg paths skip the <base> tag and fail when served
from a subpath like /server/. Now uses config.basePath in TSX and a
relative href in index.html so the <base> tag resolves correctly.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/components/LayoutShell.tsx

@@ -1,4 +1,5 @@
 import { Outlet, useNavigate, useLocation } from 'react-router';
+import { config } from '../config';
 import {
   AppShell,
   Sidebar,
@@ -616,7 +617,7 @@ function LayoutContent() {
 
   // --- Render -------------------------------------------------------
   const camelLogo = (
-    <img src="/favicon.svg" alt="" style={{ width: 28, height: 24 }} />
+    <img src={`${config.basePath}favicon.svg`} alt="" style={{ width: 28, height: 24 }} />
   );
 
   const sidebarElement = (