refactor(backend): 添加 service 缓存端口

backend/internal/service/ports/api_key_cache.go

@@ -0,0 +1,16 @@
+package ports
+
+import (
+	"context"
+	"time"
+)
+
+// ApiKeyCache defines cache operations for API key service
+type ApiKeyCache interface {
+	GetCreateAttemptCount(ctx context.Context, userID int64) (int, error)
+	IncrementCreateAttemptCount(ctx context.Context, userID int64) error
+	DeleteCreateAttemptCount(ctx context.Context, userID int64) error
+
+	IncrementDailyUsage(ctx context.Context, apiKey string) error
+	SetDailyUsageExpiry(ctx context.Context, apiKey string, ttl time.Duration) error
+}