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/auth/LoginPage.tsx

@@ -85,7 +85,7 @@ export function LoginPage() {
       <Card className={styles.card}>
         <div className={styles.loginForm}>
           <div className={styles.logo}>
-            <img src="/favicon.svg" alt="" className={styles.logoImg} />
+            <img src={`${config.basePath}favicon.svg`} alt="" className={styles.logoImg} />
             cameleer3
           </div>
           <p className={styles.subtitle}>{subtitle}</p>