제공해주신 최신 CSS 코드를 바탕으로, SNB 서브 메뉴(#shSnb)의 활성화 탭(li.on)이 아래쪽으로 자연스럽게 라운딩되어 튀어나오는 UI를完璧하게 보정한 전체 CSS 코드입니다.

수정 반영 사항
#shSnb 구조 개선: overflow: hidden을 완전히 제거하고, padding: 6px 환경에서 선택된 탭(li.on a)의 4면 모서리(border-radius: 8px)와 그림자가 잘리지 않고 온전히 나타나도록 수정했습니다.

구분선 겹침 보정: 기존 border-left 대신 가상 요소(::before)를 사용하여 li.on 바로 옆 구분선이 하얀 배경 위로 보이지 않고 자연스럽게 사라지도록 처리했습니다.

요청해주신 최신 전면 수정본 적용: Pretendard 최신 CDN, 퀵 문의 플로팅 버튼, 반응형 푸터, 카테고리 탭 flex-wrap 등 수정해주신 전반적인 리팩토링 항목을 완전히 유지했습니다.

완성된 전체 CSS 코드
CSS
@charset "utf-8";

/* Pretendard & Google Font Import */
@import url('https://cdn.jsdelivr.net/gh/orioncactus/pretendard@v1.3.9/dist/web/static/pretendard.min.css');
@import url('https://fonts.googleapis.com/css2?family=Outfit:wght@100..900&display=swap');

/* Default Reset & Base Settings */
*, *::before, *::after {
    box-sizing: border-box;
    -webkit-text-size-adjust: none;
}

body {
    margin: 0;
    padding: 0;
    background: #fff;
    font-size: 14px;
    font-family: 'Pretendard', -apple-system, BlinkMacSystemFont, system-ui, Roboto, 'Helvetica Neue', 'Segoe UI', 'Apple SD Gothic Neo', 'Noto Sans KR', 'Malgun Gothic', sans-serif;
    color: #333;
}

h1, h2, h3, h4, h5, h6, input, button, textarea, select {
    font-family: 'Pretendard', 'Outfit', sans-serif;
}

figure {
    margin: 0;
}

:root {
    --primary: #02105a;
    --k-font: 'Pretendard';
    --e-font: 'Outfit';
}

/* Quick Inquiry Floating Button */
#fix_inq {
    position: fixed;
    right: 0;
    top: 80px;
    z-index: 20;
    width: 65px;
    height: 190px;
    padding-top: 25px;
    border-radius: 12px 0 0 12px;
    color: #fff;
    text-align: center;
    background: var(--primary);
    transition: all 0.2s ease-in-out;
}

#fix_inq span {
    position: absolute;
    left: -18px;
    top: 100px;
    transform: rotate(90deg);
    font-size: 14px;
    font-weight: 500;
    white-space: nowrap;
    transition: all 0.2s ease-in-out;
    letter-spacing: 0.7px;
    font-family: var(--e-font);
}

#fix_inq i {
    font-variation-settings: 'FILL' 1, 'wght' 200, 'GRAD' 0, 'opsz' 24;
}

@media (hover: hover) {
    #fix_inq:hover {
        width: 75px;
    }
    #fix_inq:hover span {
        left: -12px;
    }
}

/* HEADER */
#sh_hd {
    position: fixed;
    left: 0;
    top: 0;
    bottom: 0;
    z-index: 25;
    width: 260px;
    font-size: 15px;
    background: #fff;
    box-shadow: 4px 0px 5px 0px rgba(0,0,0,0.07);
    font-family: var(--e-font), var(--k-font);
}

/* MAIN & CONTAINER */
#sh_section {
    overflow: hidden;
    position: relative;
    font-size: 16px;
    font-weight: 500;
    line-height: 1.65;
    color: #777;
    font-family: var(--e-font), var(--k-font);
}

#sh_section * {
    word-break: keep-all;
    overflow-wrap: break-word;
}

#sh_container {
    overflow: hidden;
    position: relative;
    z-index: 10;
    padding-left: 260px;
}

#sh_content {
    overflow: hidden;
    position: relative;
    z-index: 10;
    width: 100%;
    max-width: 1200px;
    min-height: 550px;
    padding: 70px 0;
    margin: 0 auto;
    background: #fff;
}

/* --------------------------------------------------
   SNB (서브 메뉴) 스타일 - 모서리 잘림 방지 및 구분선 보정
-------------------------------------------------- */
#shSnb {
    display: flex;
    justify-content: center;
    align-items: center;
    margin: 0 auto 50px;
    background: var(--primary);
    border-radius: 12px;
    padding: 6px;
    position: relative;
    list-style: none;
}

#shSnb li {
    position: relative;
    list-style: none;
}

/* 메뉴 구분선 (선택된 항목 앞뒤는 안 보이게 처리) */
#shSnb li + li::before {
    content: '';
    position: absolute;
    left: 0;
    top: 50%;
    transform: translateY(-50%);
    width: 1px;
    height: 18px;
    background: rgba(255, 255, 255, 0.2);
    transition: opacity 0.2s ease;
}

/* 선택된 탭 및 바로 뒤 탭의 왼쪽 구분선 숨김 */
#shSnb li.on::before,
#shSnb li.on + li::before {
    opacity: 0;
}

#shSnb li a {
    display: flex;
    align-items: center;
    justify-content: center;
    min-width: 150px;
    height: 52px;
    padding: 0 20px;
    font-size: 17px;
    font-weight: 500;
    color: #fff;
    text-decoration: none;
    border-radius: 8px;
    transition: all 0.2s ease;
}

/* 선택(활성화)된 탭 스타일 */
#shSnb li.on a {
    font-weight: 600;
    color: var(--primary);
    background: #fff;
    border-radius: 8px; /* 4개 모서리가 선명하게 둥글게 나타남 */
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15); /* 하단 돌출 입체감 강화 */
}

/* --------------------------------------------------
   게시판 카테고리 탭 (공지사항 / 문의사항)
-------------------------------------------------- */
#bo_cate_ul_line,
.sh_tab_menu {
    display: flex;
    justify-content: center;
    align-items: center;
    flex-wrap: wrap;
    list-style: none;
    padding: 0;
    margin: 0 0 30px 0;
    gap: 10px;
}

#bo_cate_ul_line li {
    display: inline-block;
}

#bo_cate_ul_line li a {
    display: block;
    padding: 12px 30px;
    font-size: 16px;
    font-weight: 500;
    color: #475569;
    background-color: #f8fafc;
    border: 1px solid #e2e8f0;
    border-radius: 8px;
    text-decoration: none;
    transition: all 0.2s ease;
}

#bo_cate_ul_line li a:hover {
    background-color: #f1f5f9;
    color: #0f172a;
}

#bo_cate_ul_line li.on a,
#bo_cate_ul_line li a.active,
#bo_cate_ul_line #bo_cate_on {
    background-color: var(--primary);
    color: #ffffff;
    border-color: var(--primary);
    font-weight: 600;
}

/* FOOTER */
#sh_ft {
    padding: 100px 80px 100px 340px;
    font-size: 16px;
    font-weight: 400;
    color: #fff;
    line-height: 1.65;
    background: #13274d;
    font-family: var(--e-font), var(--k-font);
}

#sh_ft .flex {
    display: flex;
    justify-content: space-between;
}

#sh_ft .info ul {
    margin: 50px 0;
    padding: 0;
    list-style: none;
}

#sh_ft .info ul li {
    display: flex;
    align-items: baseline;
}

#sh_ft .info ul li + li {
    margin-top: 10px;
}

#sh_ft .info ul li span {
    opacity: 0.3;
    width: 110px;
    font-weight: 600;
}

#sh_ft .info .links {
    display: flex;
}

#sh_ft .info .links a {
    padding: 10px 18px;
    font-size: 12px;
    font-weight: 600;
    color: rgba(255, 255, 255, 0.3);
    line-height: 1;
    background: rgba(255, 255, 255, 0.1);
    text-decoration: none;
}

#sh_ft .info .links a + a {
    margin-left: 4px;
}

#sh_ft .ft_mn {
    display: flex;
    padding: 0;
    list-style: none;
}

#sh_ft .ft_mn > li + li {
    margin-left: 70px;
}

#sh_ft .ft_mn > li > a {
    font-size: 18px;
    font-weight: 600;
    text-decoration: none;
}

#sh_ft .ft_mn li a {
    color: #fff;
}

#sh_ft .ft_mn li ul {
    margin-top: 20px;
    padding: 0;
    list-style: none;
}

#sh_ft .ft_mn li ul li + li {
    margin-top: 10px;
}

#sh_ft .ft_mn li ul a {
    opacity: 0.3;
    text-decoration: none;
    transition: all 0.3s;
}

#sh_ft .ft_mn li ul a:hover {
    opacity: 1;
}

#sh_ft .copy {
    display: flex;
    justify-content: space-between;
    margin-top: 65px;
    padding-top: 40px;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    font-size: 15px;
    color: rgba(255, 255, 255, 0.3);
}

#sh_ft .toTop {
    cursor: pointer;
    width: 70px;
    height: 70px;
    color: rgba(255, 255, 255, 0.4);
    text-align: center;
    line-height: 70px;
    background: rgba(255, 255, 255, 0.1);
    transition: all 0.3s;
    display: flex;
    align-items: center;
    justify-content: center;
}

#sh_ft .toTop svg {
    width: 32px;
    height: 32px;
}

#sh_ft .toTop:hover {
    color: #fff;
    background: var(--primary);
}

/* 반응형 사이트맵 공통 */
#sh_site_map {
    position: relative;
    width: 100%;
}

#sh_site_map::after {
    display: block;
    content: "";
    clear: both;
}

#sh_site_map > div {
    width: 31%;
    float: left;
    margin: 0 1%;
}

#sh_site_map > div:nth-of-type(3n) {
    margin-right: 0;
}

#sh_site_map .sh_site_map_title {
    padding: 10px 15px;
    border-bottom: 2px solid #333;
    font-size: 17px;
    font-weight: bold;
    text-align: center;
    color: #222;
}

#sh_site_map ul {
    padding: 0 15px 15px;
    list-style: none;
}

#sh_site_map .sh_site_map_box {
    min-height: 205px;
    padding: 17px 20px;
    border: 1px solid #e1e1e1;
    border-top: none;
    font-size: 14px;
    color: #333;
    line-height: 40px;
}

#sh_site_map .sh_site_map_box li {
    border-bottom: 1px dotted #ccc;
}

#sh_site_map .sh_site_map_box li:last-child {
    border: none;
}

/* 반응형 하단 버튼 공통 */
#fix_tel {
    opacity: 0;
    display: none;
    position: fixed;
    right: 15px;
    bottom: 60px;
    z-index: 101;
    width: 65px;
    height: 65px;
    margin-right: -10px;
    border-radius: 50%;
    font-size: 30px;
    text-align: center;
    line-height: 65px;
    color: #fff;
    background: var(--primary);
    box-shadow: 5px 5px 5px rgba(0, 0, 0, 0.2);
    transition: all 0.2s;
    text-decoration: none;
}

#fix_tel.active {
    opacity: 1;
    margin-right: 0;
}

#sh_ft_btns {
    display: none;
    padding: 15px;
}

#sh_ft_btns .btns {
    overflow: hidden;
}

#sh_ft_btns .row2 a {
    width: 50%;
}

#sh_ft_btns a {
    float: left;
    display: block;
    width: 100%;
    height: 55px;
    font-size: 16px;
    line-height: 55px;
    color: #fff;
    text-align: center;
    background: var(--primary);
    font-weight: bold;
    text-decoration: none;
}

#sh_ft_btns a.tel {
    font-size: 18px;
    font-weight: 700;
    letter-spacing: 0;
    font-family: 'Outfit', sans-serif;
}

#sh_ft_btns a i {
    padding-right: 5px;
    font-size: 18px;
}

#sh_ft_btns a.kakao {
    font-weight: normal;
    color: #402325;
    background-color: #ffe500;
}

/* --------------------------------------------------
   반응형 [Media Queries]
-------------------------------------------------- */
@media (max-width: 1320px) {
    #sh_ft {
        padding: 80px 50px 80px 310px;
    }
}

@media (max-width: 1024px) {
    #sh_hd {
        position: relative;
        width: 100%;
        box-shadow: none;
    }
    #sh_container {
        margin: 0;
        padding: 0;
    }
    #sh_section {
        font-size: 14px;
    }
    #sh_content {
        margin: 0 auto;
        padding: 30px 15px;
        border: none;
    }
    #shSnb {
        display: none;
    }
    #sh_ft {
        padding: 50px 20px;
    }
    #sh_ft .flex {
        flex-direction: column;
    }
    #sh_ft .info ul {
        margin: 30px 0;
    }
    #sh_ft .info ul li {
        word-break: keep-all;
    }
    #sh_ft .copy {
        margin-top: 30px;
        padding-top: 30px;
    }
    #sh_ft .toTop {
        width: 40px;
        height: 40px;
    }
    #sh_ft .toTop svg {
        width: 22px;
        height: 22px;
    }
    #sh_ft .ft_mn {
        display: none;
    }
}

@media (max-width: 768px) {
    #sh_login, #sh_agree, #sh_register, #sh_mb_confirm, #sh_result {
        padding: 15px;
        margin: 15px auto;
        border: none;
    }
    #sh_login input[type=submit], 
    #sh_agree .btn_wrap input[type=submit], 
    #sh_register .btn_wrap input[type=submit], 
    #sh_find_info input[type=submit], 
    #sh_mb_confirm input[type=submit] {
        -webkit-appearance: none;
        appearance: none;
    }
    #sh_login .bnr .txt p a {
        color: #0054a6;
    }
    #sh_pw_confirm {
        width: 100%;
        padding: 30px 20px;
        border: none;
    }
    #sh_agree .inner {
        padding: 15px;
    }
    #sh_agree .cont {
        padding: 10px;
    }
    #sh_site_map {
        padding: 30px 20px;
    }
    #sh_site_map > div {
        width: 100%;
        margin: 0 0 20px 0;
    }
    #sh_site_map .sh_site_map_box {
        min-height: auto;
    }
    
    /* Quick Inquiry Mobile Fix */
    #fix_inq {
        top: auto;
        bottom: 135px;
        right: 15px;
        width: 60px;
        height: 60px;
        padding-top: 0;
        display: flex;
        align-items: center;
        justify-content: center;
        border-radius: 50%;
        box-shadow: 2px 4px 10px rgba(0, 0, 0, 0.2);
    }
    #fix_inq span {
        display: none;
    }
    #fix_inq i {
        font-size: 28px;
    }
    
    #sh_ft {
        padding: 30px 20px;
        font-size: 15px;
    }
    #sh_ft .info ul li span {
        flex-shrink: 0;
        width: 80px;
        font-size: 14px;
    }
    
    #bo_cate_ul_line li a {
        padding: 10px 18px;
        font-size: 14px;
    }
}

@media (max-width: 480px) {
    #fix_tel {
        display: block;
    }
    #sh_ft_btns {
        display: block;
    }
    #sh_ft {
        font-size: 14px;
    }
    #sh_ft .info ul li span {
        width: 75px;
        font-size: 13px;
    }
    #sh_ft .info .links a {
        padding: 8px 15px;
        font-size: 11px;
    }
    #sh_ft .copy {
        font-size: 13px;
        flex-direction: column;
        align-items: center;
        gap: 15px;
        text-align: center;
    }
    #sh_ft .copy .links {
        float: none;
    }
}