refactor(css): 단일 style.css 를 역할별 파일로 분할 + Pretendard 로컬 호스팅

public/css/{tokens,base,layout,components,modal}.css 로 분리하고 _header 에서 다중 link 로드.
tokens.css 에 Pretendard @font-face(public/fonts/PretendardVariable.woff2, 없으면 시스템 폰트 폴백).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

public/css/layout.css

@@ -0,0 +1,71 @@
+/* 골격 — 헤더 · 메인/섹션 · 푸터. */
+
+/* ===================== 헤더 ===================== */
+.hdr { position: sticky; top: 0; z-index: 300; background: var(--hbg); border-bottom: 1px solid var(--hbd); }
+.hdr-inner { max-width: 1180px; margin: 0 auto; padding: 0 24px; height: 60px; display: flex; align-items: center; gap: 16px; }
+.brand { display: flex; align-items: center; gap: 10px; cursor: pointer; user-select: none; flex: 0 0 auto; }
+.brand-mark { display: inline-flex; color: var(--hfg); transition: transform .2s ease, filter .2s ease; }
+.brand-name { font-weight: 800; font-size: 15px; letter-spacing: .13em; color: var(--hfg); }
+.brand-sub { font-size: 11px; color: var(--hfg2); font-weight: 500; border-left: 1px solid var(--hbd); padding-left: 10px; margin-left: 2px; white-space: nowrap; }
+
+.hdr-search { flex: 1; max-width: 300px; position: relative; display: flex; align-items: center; }
+.hdr-search-ico { position: absolute; left: 10px; display: inline-flex; color: var(--hfg2); pointer-events: none; }
+.hdr-search input {
+  width: 100%; font-family: inherit; font-size: 13px; color: var(--hfg);
+  background: var(--hsearch-bg); border: 1px solid var(--hsearch-bd); border-radius: 7px;
+  padding: 6px 10px 6px 32px; outline: none;
+}
+.hdr-search input:focus { border-color: var(--link); background: var(--bg); color: var(--fg); }
+.hdr-search input::-webkit-search-cancel-button { filter: invert(.5); }
+
+.hdr-right { display: flex; align-items: center; gap: 10px; flex: 0 0 auto; margin-left: auto; }
+.icon-btn {
+  width: 32px; height: 32px; border-radius: 8px; border: 1px solid var(--hbd); background: transparent;
+  cursor: pointer; display: inline-flex; align-items: center; justify-content: center; color: var(--hfg2);
+  transition: background .14s ease, color .14s ease;
+}
+.icon-btn:hover { background: rgba(255,255,255,.08); color: var(--hfg); }
+.theme-ico-sun { display: none; }
+html[data-aidev-theme="dark"] .theme-ico-moon { display: none; }
+html[data-aidev-theme="dark"] .theme-ico-sun { display: inline-flex; }
+
+.admin-pill {
+  display: inline-flex; align-items: center; gap: 5px; font-size: 12px; font-weight: 600;
+  color: #fff; background: color-mix(in srgb, var(--admin) 80%, transparent);
+  border: 1px solid var(--hbd); border-radius: 999px; padding: 4px 11px; white-space: nowrap;
+}
+
+.usermenu { position: relative; }
+.usermenu-btn {
+  display: flex; align-items: center; gap: 8px; background: transparent; border: 1px solid transparent;
+  border-radius: 8px; padding: 4px 6px 4px 8px; cursor: pointer; font-family: inherit;
+}
+.usermenu-btn:hover { background: rgba(255,255,255,.08); }
+.usermenu-btn .who { font-size: 13px; font-weight: 600; color: var(--hfg); font-variant-numeric: tabular-nums; }
+.usermenu-btn .caret { display: inline-flex; color: var(--hfg2); }
+.usermenu-pop {
+  position: absolute; top: 46px; right: 0; width: 212px; background: var(--card); border: 1px solid var(--border);
+  border-radius: 10px; box-shadow: 0 8px 24px var(--shadow-strong); padding: 6px; z-index: 320; animation: aidev-pop .14s ease-out;
+}
+.usermenu-pop[hidden] { display: none; }
+.usermenu-head { padding: 8px 10px 10px; border-bottom: 1px solid var(--divider); margin-bottom: 6px; }
+.usermenu-label { font-size: 12px; color: var(--fg2); }
+.usermenu-sabun { font-size: 13.5px; font-weight: 600; color: var(--fg); font-variant-numeric: tabular-nums; }
+.usermenu-role { font-size: 11.5px; color: var(--fg2); margin-top: 2px; }
+.usermenu-item { width: 100%; text-align: left; background: transparent; border: 0; border-radius: 6px; padding: 8px 10px; cursor: pointer; font-family: inherit; font-size: 13px; color: var(--fg); display: flex; align-items: center; gap: 8px; }
+.usermenu-item:hover { background: var(--panel); }
+.usermenu-ico { display: inline-flex; color: var(--fg2); }
+
+/* ===================== 메인 / 섹션 ===================== */
+.main { max-width: 1180px; margin: 0 auto; padding: 32px 24px 64px; }
+.section { margin-bottom: 40px; }
+.section-head { display: flex; align-items: baseline; justify-content: space-between; gap: 12px; margin-bottom: 16px; }
+.section-titlewrap { display: flex; align-items: baseline; gap: 10px; }
+.section-title { margin: 0; font-size: 18px; font-weight: 700; color: var(--fg); letter-spacing: -.01em; }
+.section-sub { font-size: 13px; color: var(--fg2); }
+
+/* ===================== 푸터 ===================== */
+.footer { border-top: 1px solid var(--border-soft); }
+.footer-inner { max-width: 1180px; margin: 0 auto; padding: 20px 24px 28px; display: flex; align-items: center; justify-content: space-between; gap: 16px; flex-wrap: wrap; }
+.footer-brand { display: flex; align-items: center; gap: 8px; color: var(--fg3); font-size: 12px; }
+.footer-tech { font-size: 11.5px; color: var(--fg3); font-family: 'SF Mono', ui-monospace, Menlo, monospace; }