feat(ui): use bundled app icon as favicon; remove legacy vite/tauri icons\n\n- Remove <link rel=icon> pointing to /vite.svg in index.html\n- Programmatically set favicon to bundled asterisk-logo.png in src/main.tsx\n- Delete unused public icons: vite.svg and tauri.svg\n\nRationale: keeps assets bundled, avoids reliance on /public, and aligns app branding.