refactor(grpc): restructure task handling and migrate to slog

Refactor the gRPC client and task handling logic to improve modularity,
error handling, and observability.

- Split `grpc/handler.go` into specialized handler files (login,
  classroom, exams, grades, schedule) to reduce complexity.
- Replace standard `log` with `log/slog` throughout the project for
  structured logging.
- Refactor `grpc/client.go` to use a thread-safe connection management
  pattern with `sync.RWMutex`.
- Remove the legacy `service` package and HTTP server implementation,
  transitioning the application to a pure gRPC runner mode.
- Clean up `config` and `pkg/errors` to remove unused utilities and
  simplify the API.
- Improve error reporting in parsers and HTTP clients by checking
  response status codes.

captcha/recognize.go

@@ -3,20 +3,15 @@ package captcha
 import (
 	"fmt"
 	"io"
+	"log/slog"
 	"net/http"
-	"os"
-	"strings"
 
 	"schedule_converter/client"
 	"schedule_converter/config"
-
-	"github.com/PuerkitoBio/goquery"
 )
 
 func SaveCaptchaImage(httpClient *http.Client) ([]byte, error) {
-	fmt.Println("[2] 获取验证码...")
-
-	req, err := http.NewRequest("GET", config.BaseURL+"/captchaImage", nil)
+	req, err := http.NewRequest("GET", config.Get().BaseURL+"/captchaImage", nil)
 	if err != nil {
 		return nil, err
 	}
@@ -28,25 +23,18 @@ func SaveCaptchaImage(httpClient *http.Client) ([]byte, error) {
 	}
 	defer resp.Body.Close()
 
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("获取验证码失败, 状态码: %d", resp.StatusCode)
+	}
+
 	body, err := io.ReadAll(resp.Body)
 	if err != nil {
 		return nil, err
 	}
 
-	if err := os.WriteFile("captcha.png", body, 0644); err != nil {
-		fmt.Printf("    警告: 无法保存验证码图片: %v\n", err)
-	} else {
-		fmt.Println("    验证码已保存到: captcha.png")
-	}
-
 	return body, nil
 }
 
-func Recognize(imagePath string) (string, error) {
-	fmt.Println("[3] 使用固定验证码...")
-	return "....", nil
-}
-
 func GetAndRecognize(httpClient *http.Client) (string, error) {
 	_, err := SaveCaptchaImage(httpClient)
 	if err != nil {
@@ -58,10 +46,10 @@ func GetAndRecognize(httpClient *http.Client) (string, error) {
 		return "", err
 	}
 
-	fmt.Printf("    识别结果: %s\n", captchaCode)
+	slog.Debug("验证码识别完成", "result", captchaCode)
 	return captchaCode, nil
 }
 
-func ParseHTML(html string) (*goquery.Document, error) {
-	return goquery.NewDocumentFromReader(strings.NewReader(html))
-}
+func Recognize(imagePath string) (string, error) {
+	return "....", nil
+}