diff --git a/docs/code-improvements.md b/docs/code-improvements.md
index 3b85c15..a401b5f 100644
--- a/docs/code-improvements.md
+++ b/docs/code-improvements.md
@@ -640,12 +640,14 @@ closeConfirm: () => ...,
 
 ---
 
-## 3. 중간 우선순위 (Medium)
+## 3. 중간 우선순위 (Medium) ✅ 완료
 
-### 3.1 API 에러 처리 불일치
+### 3.1 API 에러 처리 불일치 ✅
 
 **파일**: `api/client.js`
 
+**상태**: ✅ 완료 - `fetchFormData`에 `requireAuth` 옵션 추가
+
 **문제**:
 ```javascript
 // fetchAuthApi - 토큰 없으면 에러 발생
@@ -688,10 +690,12 @@ export async function fetchFormData(endpoint, formData, method = 'POST', { requi
 
 ---
 
-### 3.2 HTTP 헬퍼 함수 중복
+### 3.2 HTTP 헬퍼 함수 중복 ✅
 
 **파일**: `api/client.js`
 
+**상태**: ✅ 완료 - `createMethodHelpers` 팩토리 함수로 통합, `api`/`authApi` 객체 export
+
 **문제**:
 ```javascript
 // 8개의 유사한 헬퍼 함수
@@ -736,10 +740,12 @@ export const authApi = createMethodHelpers(fetchAuthApi);
 
 ---
 
-### 3.3 useMediaQuery 리스너 메모이제이션
+### 3.3 useMediaQuery 리스너 메모이제이션 ✅
 
 **파일**: `hooks/useMediaQuery.js`
 
+**상태**: ✅ 완료 - `useCallback`으로 핸들러 메모이제이션
+
 **문제**:
 ```javascript
 useEffect(() => {
@@ -780,10 +786,12 @@ export function useMediaQuery(query) {
 
 ---
 
-### 3.4 useCalendar 반환 객체 메모이제이션
+### 3.4 useCalendar 반환 객체 메모이제이션 ✅
 
 **파일**: `hooks/useCalendar.js`
 
+**상태**: ✅ 완료 - `useMemo`로 반환 객체 메모이제이션
+
 **문제**:
 ```javascript
 return {
@@ -825,10 +833,12 @@ return useMemo(() => ({
 
 ---
 
-### 3.5 날짜/시간 추출 함수 중복
+### 3.5 날짜/시간 추출 함수 중복 ✅
 
 **파일**: `utils/date.js`, `utils/schedule.js`
 
+**상태**: ✅ 완료 - `schedule.js`에서 `date.js`의 `extractDate`, `extractTime` 재사용
+
 **중복 함수**:
 ```javascript
 // date.js
@@ -858,10 +868,12 @@ export function getScheduleTime(schedule) {
 
 ---
 
-### 3.6 decodeHtmlEntities DOM 조작
+### 3.6 decodeHtmlEntities DOM 조작 ✅
 
 **파일**: `utils/format.js`
 
+**상태**: ✅ 완료 - 순수 함수로 변경 (정규식 + 매핑 객체), SSR 호환
+
 **문제**:
 ```javascript
 export function decodeHtmlEntities(text) {
diff --git a/frontend-temp/src/api/client.js b/frontend-temp/src/api/client.js
index 39e7d8d..4110687 100644
--- a/frontend-temp/src/api/client.js
+++ b/frontend-temp/src/api/client.js
@@ -87,11 +87,17 @@ export async function fetchAuthApi(endpoint, options = {}) {
  * @param {string} endpoint - API 엔드포인트
  * @param {FormData} formData - 전송할 FormData
  * @param {string} method - HTTP 메서드 (기본: POST)
+ * @param {Object} options - 추가 옵션
+ * @param {boolean} options.requireAuth - 인증 필수 여부 (기본: true)
  */
-export async function fetchFormData(endpoint, formData, method = 'POST') {
+export async function fetchFormData(endpoint, formData, method = 'POST', { requireAuth = true } = {}) {
   const token = useAuthStore.getState().token;
   const url = endpoint.startsWith('/api') ? endpoint : `${API_BASE}${endpoint}`;
 
+  if (requireAuth && !token) {
+    throw new ApiError('인증이 필요합니다.', 401);
+  }
+
   const headers = {};
   if (token) {
     headers.Authorization = `Bearer ${token}`;
@@ -107,46 +113,43 @@ export async function fetchFormData(endpoint, formData, method = 'POST') {
 }
 
 /**
- * GET 요청 헬퍼
+ * HTTP 메서드 헬퍼 생성기
  */
-export const get = (endpoint) => fetchApi(endpoint);
-export const authGet = (endpoint) => fetchAuthApi(endpoint);
+function createMethodHelpers(baseFetch) {
+  return {
+    get: (endpoint) => baseFetch(endpoint),
+    post: (endpoint, data) =>
+      baseFetch(endpoint, {
+        method: 'POST',
+        body: JSON.stringify(data),
+      }),
+    put: (endpoint, data) =>
+      baseFetch(endpoint, {
+        method: 'PUT',
+        body: JSON.stringify(data),
+      }),
+    del: (endpoint) => baseFetch(endpoint, { method: 'DELETE' }),
+  };
+}
 
 /**
- * POST 요청 헬퍼
+ * 공개 API 헬퍼
+ * @example api.get('/albums'), api.post('/albums', data)
  */
-export const post = (endpoint, data) =>
-  fetchApi(endpoint, {
-    method: 'POST',
-    body: JSON.stringify(data),
-  });
-
-export const authPost = (endpoint, data) =>
-  fetchAuthApi(endpoint, {
-    method: 'POST',
-    body: JSON.stringify(data),
-  });
+export const api = createMethodHelpers(fetchApi);
 
 /**
- * PUT 요청 헬퍼
+ * 인증 API 헬퍼
+ * @example authApi.get('/admin/stats'), authApi.post('/admin/schedules', data)
  */
-export const put = (endpoint, data) =>
-  fetchApi(endpoint, {
-    method: 'PUT',
-    body: JSON.stringify(data),
-  });
+export const authApi = createMethodHelpers(fetchAuthApi);
 
-export const authPut = (endpoint, data) =>
-  fetchAuthApi(endpoint, {
-    method: 'PUT',
-    body: JSON.stringify(data),
-  });
-
-/**
- * DELETE 요청 헬퍼
- */
-export const del = (endpoint) =>
-  fetchApi(endpoint, { method: 'DELETE' });
-
-export const authDel = (endpoint) =>
-  fetchAuthApi(endpoint, { method: 'DELETE' });
+// 기존 호환성을 위한 개별 export (점진적 마이그레이션 후 삭제 예정)
+export const get = api.get;
+export const post = api.post;
+export const put = api.put;
+export const del = api.del;
+export const authGet = authApi.get;
+export const authPost = authApi.post;
+export const authPut = authApi.put;
+export const authDel = authApi.del;
diff --git a/frontend-temp/src/hooks/useCalendar.js b/frontend-temp/src/hooks/useCalendar.js
index 8a2e190..d645304 100644
--- a/frontend-temp/src/hooks/useCalendar.js
+++ b/frontend-temp/src/hooks/useCalendar.js
@@ -89,16 +89,30 @@ export function useCalendar(initialDate = new Date()) {
     [year, month]
   );
 
-  return {
-    ...calendarData,
-    currentDate,
-    selectedDate,
-    canGoPrevMonth,
-    goToPrevMonth,
-    goToNextMonth,
-    goToMonth,
-    goToToday,
-    selectDate,
-    setSelectedDate,
-  };
+  // 반환 객체 메모이제이션
+  return useMemo(
+    () => ({
+      ...calendarData,
+      currentDate,
+      selectedDate,
+      canGoPrevMonth,
+      goToPrevMonth,
+      goToNextMonth,
+      goToMonth,
+      goToToday,
+      selectDate,
+      setSelectedDate,
+    }),
+    [
+      calendarData,
+      currentDate,
+      selectedDate,
+      canGoPrevMonth,
+      goToPrevMonth,
+      goToNextMonth,
+      goToMonth,
+      goToToday,
+      selectDate,
+    ]
+  );
 }
diff --git a/frontend-temp/src/hooks/useMediaQuery.js b/frontend-temp/src/hooks/useMediaQuery.js
index 09a4986..5e6f390 100644
--- a/frontend-temp/src/hooks/useMediaQuery.js
+++ b/frontend-temp/src/hooks/useMediaQuery.js
@@ -1,4 +1,4 @@
-import { useState, useEffect } from 'react';
+import { useState, useEffect, useCallback } from 'react';
 
 /**
  * 미디어 쿼리 훅
@@ -13,14 +13,19 @@ export function useMediaQuery(query) {
     return false;
   });
 
-  // DOM 이벤트 리스너이므로 useEffect 사용 허용
+  // 핸들러 메모이제이션
+  const handler = useCallback((e) => {
+    setMatches(e.matches);
+  }, []);
+
+  // DOM 이벤트 리스너
   useEffect(() => {
     const mediaQuery = window.matchMedia(query);
-    const handler = (e) => setMatches(e.matches);
+    setMatches(mediaQuery.matches);
 
     mediaQuery.addEventListener('change', handler);
     return () => mediaQuery.removeEventListener('change', handler);
-  }, [query]);
+  }, [query, handler]);
 
   return matches;
 }
diff --git a/frontend-temp/src/utils/format.js b/frontend-temp/src/utils/format.js
index 031600a..48f46ff 100644
--- a/frontend-temp/src/utils/format.js
+++ b/frontend-temp/src/utils/format.js
@@ -3,15 +3,30 @@
  */
 
 /**
- * HTML 엔티티 디코딩
+ * HTML 엔티티 매핑
+ */
+const HTML_ENTITIES = {
+  '&': '&',
+  '&lt;': '<',
+  '&gt;': '>',
+  '&quot;': '"',
+  '&#39;': "'",
+  '&apos;': "'",
+  '&#x27;': "'",
+  '&nbsp;': ' ',
+};
+
+/**
+ * HTML 엔티티 디코딩 (순수 함수 - SSR 호환)
  * @param {string} text - HTML 엔티티가 포함된 텍스트
  * @returns {string} 디코딩된 텍스트
  */
 export const decodeHtmlEntities = (text) => {
   if (!text) return '';
-  const textarea = document.createElement('textarea');
-  textarea.innerHTML = text;
-  return textarea.value;
+  return text.replace(
+    /&(?:amp|lt|gt|quot|#39|apos|#x27|nbsp);/g,
+    (match) => HTML_ENTITIES[match] || match
+  );
 };
 
 /**
diff --git a/frontend-temp/src/utils/schedule.js b/frontend-temp/src/utils/schedule.js
index 5aca8d1..d974f6b 100644
--- a/frontend-temp/src/utils/schedule.js
+++ b/frontend-temp/src/utils/schedule.js
@@ -1,6 +1,7 @@
 /**
  * 스케줄 관련 유틸리티 함수
  */
+import { extractDate, extractTime } from './date';
 
 /**
  * 스케줄에서 카테고리 ID 추출
@@ -32,9 +33,7 @@ export function getCategoryInfo(schedule) {
  * @returns {string} YYYY-MM-DD 형식 날짜
  */
 export function getScheduleDate(schedule) {
-  const datetime = schedule.datetime || schedule.date;
-  if (!datetime) return '';
-  return datetime.split(' ')[0].split('T')[0];
+  return schedule.date || extractDate(schedule.datetime);
 }
 
 /**
@@ -46,14 +45,7 @@ export function getScheduleTime(schedule) {
   if (schedule.time) {
     return schedule.time.slice(0, 5);
   }
-  const datetime = schedule.datetime;
-  if (datetime && (datetime.includes(' ') || datetime.includes('T'))) {
-    const timePart = datetime.includes(' ')
-      ? datetime.split(' ')[1]
-      : datetime.split('T')[1];
-    return timePart?.slice(0, 5) || null;
-  }
-  return null;
+  return extractTime(schedule.datetime);
 }
 
 /**