refactor: replace standard log with zap logger and optimize code patterns

- Migrate all log.Printf/log.Println calls to structured zap logging
- Use cmp.Or for cleaner default value handling
- Replace manual loops with slices.ContainsFunc/IndexFunc
- Add batch query methods (IsLikedBatch, IsFavoritedBatch) to solve N+1 problem
- Update JSON tags from omitempty to omitzero for numeric fields
- Use errgroup-style wg.Go for worker goroutines
- Remove duplicate casbin/v2 dependency (keeping v3)
- Add plans/ to gitignore

internal/service/user_activity_service.go

@@ -3,10 +3,11 @@ package service
 import (
 	"context"
 	"fmt"
-	"log"
 	"time"
 
 	"carrot_bbs/internal/repository"
+
+	"go.uber.org/zap"
 )
 
 // UserActivityService 用户活跃统计服务接口
@@ -76,14 +77,18 @@ func (s *userActivityService) RecordUserActive(ctx context.Context, userID, logi
 	// 1. 记录到 Redis（同步，快速）
 	if err := s.repo.RecordActivityToRedis(ctx, userID); err != nil {
 		// 记录日志但不阻断流程
-		log.Printf("failed to record activity to redis: %v", err)
+		zap.L().Warn("failed to record activity to redis",
+			zap.Error(err),
+		)
 	}
 
 	// 2. 异步写入数据库（可以使用 goroutine 或消息队列）
 	go func() {
 		bgCtx := context.Background()
 		if err := s.repo.RecordActivity(bgCtx, userID, loginType, ip, userAgent); err != nil {
-			log.Printf("failed to record activity to db: %v", err)
+			zap.L().Warn("failed to record activity to db",
+				zap.Error(err),
+			)
 		}
 	}()
 
@@ -158,7 +163,9 @@ func (s *userActivityService) GetActivityStats(ctx context.Context) (*ActivitySt
 	// 获取今日 DAU
 	todayDAU, err := s.GetDAU(ctx, today)
 	if err != nil {
-		log.Printf("failed to get today DAU: %v", err)
+		zap.L().Warn("failed to get today DAU",
+			zap.Error(err),
+		)
 	}
 	resp.Today = DailyStats{
 		Date: today.Format("2006-01-02"),
@@ -168,7 +175,9 @@ func (s *userActivityService) GetActivityStats(ctx context.Context) (*ActivitySt
 	// 获取昨日 DAU
 	yesterdayDAU, err := s.GetDAU(ctx, yesterday)
 	if err != nil {
-		log.Printf("failed to get yesterday DAU: %v", err)
+		zap.L().Warn("failed to get yesterday DAU",
+			zap.Error(err),
+		)
 	}
 	resp.Yesterday = DailyStats{
 		Date: yesterday.Format("2006-01-02"),
@@ -178,7 +187,9 @@ func (s *userActivityService) GetActivityStats(ctx context.Context) (*ActivitySt
 	// 获取本周 WAU
 	wau, err := s.GetWAU(ctx, year, week)
 	if err != nil {
-		log.Printf("failed to get WAU: %v", err)
+		zap.L().Warn("failed to get WAU",
+			zap.Error(err),
+		)
 	}
 	resp.ThisWeek = PeriodStats{
 		Period:      fmt.Sprintf("%d-W%02d", year, week),
@@ -188,7 +199,9 @@ func (s *userActivityService) GetActivityStats(ctx context.Context) (*ActivitySt
 	// 获取本月 MAU
 	mau, err := s.GetMAU(ctx, now.Year(), int(now.Month()))
 	if err != nil {
-		log.Printf("failed to get MAU: %v", err)
+		zap.L().Warn("failed to get MAU",
+			zap.Error(err),
+		)
 	}
 	resp.ThisMonth = PeriodStats{
 		Period:      now.Format("2006-01"),
@@ -199,7 +212,9 @@ func (s *userActivityService) GetActivityStats(ctx context.Context) (*ActivitySt
 	// 次日留存
 	day1Retention, err := s.GetRetention(ctx, yesterday, today)
 	if err != nil {
-		log.Printf("failed to get day 1 retention: %v", err)
+		zap.L().Warn("failed to get day 1 retention",
+			zap.Error(err),
+		)
 	}
 	resp.Retention.Day1 = day1Retention
 
@@ -207,7 +222,9 @@ func (s *userActivityService) GetActivityStats(ctx context.Context) (*ActivitySt
 	day7Date := today.AddDate(0, 0, -7)
 	day7Retention, err := s.GetRetention(ctx, day7Date, today)
 	if err != nil {
-		log.Printf("failed to get day 7 retention: %v", err)
+		zap.L().Warn("failed to get day 7 retention",
+			zap.Error(err),
+		)
 	}
 	resp.Retention.Day7 = day7Retention
 
@@ -215,7 +232,9 @@ func (s *userActivityService) GetActivityStats(ctx context.Context) (*ActivitySt
 	day30Date := today.AddDate(0, 0, -30)
 	day30Retention, err := s.GetRetention(ctx, day30Date, today)
 	if err != nil {
-		log.Printf("failed to get day 30 retention: %v", err)
+		zap.L().Warn("failed to get day 30 retention",
+			zap.Error(err),
+		)
 	}
 	resp.Retention.Day30 = day30Retention