Add Popup Focus Trap Feature

src/app/components/popup/popup.html

@@ -1,5 +1,5 @@
 <div class="popup-backdrop" [class.center]="isCenter" (click)="$event.target === $event.currentTarget && onClose()">
-  <div class="popup-container"
+  <div #popupContainer class="popup-container"
        [class]="'variant-' + variant()"
        [class.custom-pos]="!isCenter"
        [style.top]="customStyle.top"
@@ -12,7 +12,7 @@
       </div>
 
       <div class="header-right">
-        <button class="material-symbols-outlined icon-24 close-btn" (click)="onClose()">close</button>
+        <button class="material-symbols-outlined icon-24 close-btn" (click)="onClose()" [aria-label]="closeButtonLabel()">close</button>
       </div>
     </header>
 

src/app/components/popup/popup.scss

@@ -52,6 +52,11 @@ $default_animation_duration: 0.2s;
   &.custom-pos {
     position: absolute;
   }
+
+  &:focus-visible {
+    outline-offset: 0;
+    outline: 2px solid var(--selection-outline-color);
+  }
 }
 
 @keyframes popup-enter {

src/app/components/popup/popup.ts

@@ -1,4 +1,15 @@
-import { Component, input, output, HostListener } from '@angular/core';
+import {
+  Component,
+  input,
+  output,
+  HostListener,
+  ElementRef,
+  inject,
+  viewChild,
+  OnInit,
+  OnDestroy,
+} from '@angular/core';
+import { TranslationService } from '../../services/translation.service';
 
 export type PopupPosition = {
   top?: string;
@@ -15,12 +26,16 @@ export type PopupVariant = 'glass' | 'solid';
   templateUrl: './popup.html',
   styleUrl: './popup.scss',
   host: {
-    'role': 'dialog',
+    role: 'dialog',
     'aria-modal': 'true',
-    'tabindex': '-1'
-  }
+    tabindex: '-1',
+  },
 })
-export class PopupComponent {
+export class PopupComponent implements OnInit, OnDestroy {
+  private translation = inject(TranslationService).translation;
+  popupContainer = viewChild<ElementRef<HTMLElement>>('popupContainer');
+  private previouslyFocusedElement: HTMLElement | null = null;
+
   /**
    * 팝업의 위치 (기본값은 'center')
    * 'center' 또는 { top, left, right, bottom } 객체를 받습니다.
@@ -32,14 +47,102 @@ export class PopupComponent {
    */
   variant = input<PopupVariant>('glass');
 
+  /**
+   * 팝업 닫기 버튼의 aria-label (기본값은 번역의 'close')
+   */
+  closeButtonLabel = input<string>(this.translation.common.close);
+
   /**
    * 팝업 닫기 요청 (배경 클릭 또는 닫기 버튼)
    */
   closeRequest = output<void>();
 
-  @HostListener('document:keydown.escape')
-  onKeydownHandler() {
-    this.onClose();
+  constructor(private element: ElementRef) {}
+
+  ngOnInit() {
+    if (typeof document !== 'undefined') {
+      this.previouslyFocusedElement = document.activeElement as HTMLElement;
+    }
+
+    setTimeout(() => {
+      this.element.nativeElement.focus();
+
+      this.popupContainer()!.nativeElement.tabIndex = 0;
+      this.popupContainer()!.nativeElement.focus();
+    }, 0);
+  }
+
+  ngOnDestroy() {
+    if (
+      this.previouslyFocusedElement &&
+      typeof this.previouslyFocusedElement.focus === 'function'
+    ) {
+      this.previouslyFocusedElement.focus();
+    }
+  }
+
+  @HostListener('keydown', ['$event'])
+  onKeydownHandler(event: KeyboardEvent) {
+    if (event.key === 'Tab') this.handleTabKey(event);
+    if (event.key === 'Escape') this.onClose();
+  }
+
+  private handleTabKey(event: KeyboardEvent) {
+    const focusableElements = this.getOrderedFocusableElements(this.popupContainer()!.nativeElement);
+
+    if (focusableElements.length === 0) {
+      event.preventDefault();
+      return;
+    }
+
+    const firstElement = focusableElements[0] as HTMLElement;
+    const lastElement = focusableElements[focusableElements.length - 1] as HTMLElement;
+    const activeElement = document.activeElement;
+
+    if (event.shiftKey) {
+      // If Shift + Tab and focus is on the first element (or the container), move to the last element
+      if (
+        activeElement === firstElement ||
+        activeElement === this.popupContainer()!.nativeElement
+      ) {
+        lastElement.focus();
+        event.preventDefault();
+      }
+    } else {
+      // If Tab and focus is on the last element, move to the first element
+      if (activeElement === lastElement) {
+        firstElement.focus();
+        event.preventDefault();
+      }
+    }
+  }
+
+  getOrderedFocusableElements(container: HTMLElement) {
+    const selector = 'button, [href], input, select, textarea, [tabindex]';
+
+    const elements = Array.from(container.querySelectorAll(selector)).filter((el) => {
+      const htmlEl = el as HTMLElement;
+
+      // 비활성 상태거나 tabindex가 -1이면 제외
+      if ((htmlEl as HTMLInputElement).disabled || el.getAttribute('tabindex') === '-1')
+        return false;
+      // 화면에 보이지 않는 요소 제외 (필요 시 추가)
+      return !!(htmlEl.offsetWidth || htmlEl.offsetHeight || el.getClientRects().length);
+    });
+
+    return elements.sort((a, b) => {
+      const tabA = parseInt(a.getAttribute('tabindex') ?? '0', 10);
+      const tabB = parseInt(b.getAttribute('tabindex') ?? '0', 10);
+
+      // 1. 양수 tabindex 처리 (낮은 숫자 우선)
+      if (tabA > 0 && tabB > 0) return tabA - tabB;
+      if (tabA > 0) return -1;
+      if (tabB > 0) return 1;
+
+      // 2. 나머지는(0 또는 기본값) DOM 순서 유지
+      // querySelectorAll 결과가 이미 DOM 순서이므로 0 반환으로 충분
+      return 0;
+    });
   }
 
   onClose() {