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/middleware/casbin.go

@@ -1,6 +1,7 @@
 package middleware
 
 import (
+	"slices"
 	"strings"
 
 	"carrot_bbs/internal/service"
@@ -104,18 +105,9 @@ func RequireRole(casbinService service.CasbinService, requiredRoles ...string) g
 		}
 
 		// 检查用户是否拥有任一所需角色
-		roleMap := make(map[string]bool)
-		for _, role := range userRoles {
-			roleMap[role] = true
-		}
-
-		hasRole := false
-		for _, required := range requiredRoles {
-			if roleMap[required] {
-				hasRole = true
-				break
-			}
-		}
+		hasRole := slices.ContainsFunc(requiredRoles, func(required string) bool {
+			return slices.Contains(userRoles, required)
+		})
 
 		if !hasRole {
 			c.AbortWithStatusJSON(403, gin.H{