fix(backend): 移除对已删除 ports 包的依赖

适配 main 分支的 ports 目录删除重构:
- 将 ports 包中的接口移至 service 包
- 更新 repository 层的导入路径

backend/internal/repository/geminicli_codeassist_client.go

@@ -6,7 +6,7 @@ import (
 	"time"
 
 	"github.com/Wei-Shaw/sub2api/internal/pkg/geminicli"
-	"github.com/Wei-Shaw/sub2api/internal/service/ports"
+	"github.com/Wei-Shaw/sub2api/internal/service"
 
 	"github.com/imroc/req/v3"
 )
@@ -15,7 +15,7 @@ type geminiCliCodeAssistClient struct {
 	baseURL string
 }
 
-func NewGeminiCliCodeAssistClient() ports.GeminiCliCodeAssistClient {
+func NewGeminiCliCodeAssistClient() service.GeminiCliCodeAssistClient {
 	return &geminiCliCodeAssistClient{baseURL: geminicli.GeminiCliBaseURL}
 }