feat: 브랜드 파비콘(SVG) 추가 — 네이비 배경·쓰레기통·에코 잎

- public/favicon.svg 신규, 관리자/인증/포털 head에 링크(기존 .ico 폴백 유지)

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

app/Views/auth/_shell.php

@@ -15,6 +15,9 @@ $subtitle = $subtitle ?? '종량제 쓰레기봉투 물류시스템';
 <meta charset="utf-8"/>
 <meta content="width=device-width, initial-scale=1.0" name="viewport"/>
 <title><?= esc($pageTitle ?? 'GBLS') ?></title>
+<link rel="icon" type="image/svg+xml" href="<?= base_url('favicon.svg') ?>"/>
+<link rel="alternate icon" href="<?= base_url('favicon.ico') ?>"/>
+<link rel="apple-touch-icon" href="<?= base_url('favicon.svg') ?>"/>
 <script src="https://cdn.tailwindcss.com?plugins=forms,container-queries"></script>
 <link rel="stylesheet" href="https://cdn.jsdelivr.net/gh/orioncactus/pretendard@v1.3.9/dist/web/static/pretendard.min.css"/>
 <link href="https://cdnjs.cloudflare.com/ajax/libs/font-awesome/6.4.0/css/all.min.css" rel="stylesheet"/>