fix: 修复多个管理后台问题

- 分页接口 page_size 最大限制从 100 改为 1000
- 通过 Redis Pub/Sub 实现跨实例认证缓存失效
- 允许订阅类型分组编辑计费倍率
- 账号计费倍率支持 3 位小数

backend/internal/service/api_key_auth_cache_impl.go

@@ -94,6 +94,20 @@ func (s *APIKeyService) initAuthCache(cfg *config.Config) {
 	s.authCacheL1 = cache
 }
 
+// StartAuthCacheInvalidationSubscriber starts the Pub/Sub subscriber for L1 cache invalidation.
+// This should be called after the service is fully initialized.
+func (s *APIKeyService) StartAuthCacheInvalidationSubscriber(ctx context.Context) {
+	if s.cache == nil || s.authCacheL1 == nil {
+		return
+	}
+	if err := s.cache.SubscribeAuthCacheInvalidation(ctx, func(cacheKey string) {
+		s.authCacheL1.Del(cacheKey)
+	}); err != nil {
+		// Log but don't fail - L1 cache will still work, just without cross-instance invalidation
+		println("[Service] Warning: failed to start auth cache invalidation subscriber:", err.Error())
+	}
+}
+
 func (s *APIKeyService) authCacheKey(key string) string {
 	sum := sha256.Sum256([]byte(key))
 	return hex.EncodeToString(sum[:])
@@ -149,6 +163,8 @@ func (s *APIKeyService) deleteAuthCache(ctx context.Context, cacheKey string) {
 		return
 	}
 	_ = s.cache.DeleteAuthCache(ctx, cacheKey)
+	// Publish invalidation message to other instances
+	_ = s.cache.PublishAuthCacheInvalidation(ctx, cacheKey)
 }
 
 func (s *APIKeyService) loadAuthCacheEntry(ctx context.Context, key, cacheKey string) (*APIKeyAuthCacheEntry, error) {