Add in-page login config modal

Allow setting Auth0 domain/clientId and allowed emails via a modal saved to localStorage to enable login testing without redeploying.

Co-authored-by: Cursor <cursoragent@cursor.com>

index.html

@@ -175,6 +175,42 @@
       </div>
     </div>
 
+    <!-- Auth Config Modal -->
+    <div class="modal" id="authModal" role="dialog" aria-modal="true" aria-labelledby="authModalTitle" hidden>
+      <div class="modal-backdrop" data-auth-close="1"></div>
+      <div class="modal-card" role="document">
+        <div class="modal-head">
+          <div class="modal-title" id="authModalTitle">로그인 설정</div>
+          <button class="icon-btn" type="button" id="btnAuthClose" title="닫기" aria-label="닫기">×</button>
+        </div>
+
+        <form id="authForm" class="modal-body">
+          <label class="field">
+            <span class="field-label">Auth0 Domain</span>
+            <input id="authDomain" class="input" type="text" placeholder="예: your-tenant.us.auth0.com" />
+            <div class="hint">Auth0 테넌트 도메인입니다. (비밀값 아님)</div>
+          </label>
+
+          <label class="field">
+            <span class="field-label">Auth0 Client ID</span>
+            <input id="authClientId" class="input" type="text" placeholder="예: AbCdEf..." />
+            <div class="hint">Auth0 SPA Application의 Client ID입니다. (비밀값 아님)</div>
+          </label>
+
+          <label class="field">
+            <span class="field-label">허용 이메일</span>
+            <input id="authAllowedEmails" class="input" type="text" placeholder="예: me@example.com, admin@example.com" />
+            <div class="hint">쉼표로 구분합니다. 비워두면 “로그인한 모든 계정”이 관리 가능해집니다.</div>
+          </label>
+
+          <div class="modal-foot">
+            <button class="btn btn-ghost" type="button" id="btnAuthReset">초기화</button>
+            <button class="btn btn-primary" type="submit" id="btnAuthSave">저장</button>
+          </div>
+        </form>
+      </div>
+    </div>
+
     <!-- Hidden file input for import -->
     <input id="file" type="file" accept="application/json" hidden />