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/handler/group_handler.go

@@ -1,10 +1,10 @@
 package handler
 
 import (
-	"log"
 	"strconv"
 
 	"github.com/gin-gonic/gin"
+	"go.uber.org/zap"
 
 	"carrot_bbs/internal/dto"
 	"carrot_bbs/internal/model"
@@ -1361,12 +1361,24 @@ func (h *GroupHandler) HandleSetGroupBan(c *gin.Context) {
 
 	// duration > 0 或 duration = -1 表示禁言，duration = 0 表示解除禁言
 	muted := params.Duration != 0
-	log.Printf("[HandleSetGroupBan] 开始禁言操作: userID=%s, groupID=%s, targetUserID=%s, duration=%d, muted=%v", userID, groupID, params.UserID, params.Duration, muted)
+	zap.L().Info("开始禁言操作",
+		zap.String("component", "HandleSetGroupBan"),
+		zap.String("userID", userID),
+		zap.String("groupID", groupID),
+		zap.String("targetUserID", params.UserID),
+		zap.Int64("duration", params.Duration),
+		zap.Bool("muted", muted),
+	)
 	err := h.groupService.MuteMember(userID, groupID, params.UserID, muted)
 	if err != nil {
-		log.Printf("[HandleSetGroupBan] 禁言操作失败: %v", err)
+		zap.L().Warn("禁言操作失败",
+			zap.String("component", "HandleSetGroupBan"),
+			zap.Error(err),
+		)
 	} else {
-		log.Printf("[HandleSetGroupBan] 禁言操作成功")
+		zap.L().Info("禁言操作成功",
+			zap.String("component", "HandleSetGroupBan"),
+		)
 	}
 	if err != nil {
 		if err == service.ErrNotGroupAdmin {