Add daily rotating recommended category endpoint

[Copilot]

Implements /api/categories/today-recommended endpoint that returns category recommendations that rotate daily but remain consistent within each day.

Implementation

• Daily rotation via deterministic shuffling: Uses LocalDate.now().toEpochDay() as Random seed to ensure same-day consistency
• Redis caching: Date-based cache key CATEGORIES:TODAY_RECOMMENDED:YYYY-MM-DD with 24h TTL
• Cache validation: Falls through to regeneration if cached list has insufficient items for requested count

Code

public List<CategorySimpleResponse> getTodayRecommendedCategories(int count) {
    LocalDate today = LocalDate.now();
    String cacheKey = CacheKeyConstants.TODAY_RECOMMENDED_CATEGORIES + ":" + today;
    
    List<CategorySimpleResponse> cached = redisCacheService.getList(cacheKey, CategorySimpleResponse.class);
    if (cached != null && cached.size() >= count) {
        return cached.stream().limit(count).collect(Collectors.toList());
    }
    
    List<Category> subCategories = categoryRepository.findAllSubCategories();
    List<Category> shuffledCategories = new ArrayList<>(subCategories);
    Collections.shuffle(shuffledCategories, new Random(today.toEpochDay()));
    
    // ... cache and return
}

API

GET /api/categories/today-recommended?count=8

• Returns: List<CategorySimpleResponse> (categoryId, name, iconUrl, displayOrder)
• Default count: 8, range: 1-100

Original prompt

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This section details on the original issue you should resolve

<issue_title>[Feat]오늘의 추천 카테고리 탭</issue_title>
<issue_description>## 📌 Description

[Feat]오늘의 추천 카테고리 탭

✅ To-do

• 진행 예정
• 진행 완료

📒 기타</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [Feat]마이페이지 -개인 프로필 #52

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