refactor(backend): 添加 service 缓存端口

backend/internal/service/ports/concurrency_cache.go

@@ -0,0 +1,19 @@
+package ports
+
+import "context"
+
+// ConcurrencyCache defines cache operations for concurrency service
+type ConcurrencyCache interface {
+	// Slot management
+	AcquireAccountSlot(ctx context.Context, accountID int64, maxConcurrency int) (bool, error)
+	ReleaseAccountSlot(ctx context.Context, accountID int64) error
+	GetAccountConcurrency(ctx context.Context, accountID int64) (int, error)
+
+	AcquireUserSlot(ctx context.Context, userID int64, maxConcurrency int) (bool, error)
+	ReleaseUserSlot(ctx context.Context, userID int64) error
+	GetUserConcurrency(ctx context.Context, userID int64) (int, error)
+
+	// Wait queue
+	IncrementWaitCount(ctx context.Context, userID int64, maxWait int) (bool, error)
+	DecrementWaitCount(ctx context.Context, userID int64) error
+}