refactor: 重构代码架构并使用 Modern Go 特性

- 重命名模块 jwts -> schedule_converter
- 新增 service 包，统一业务逻辑层
- 新增 pkg/logger 包，使用 slog 结构化日志
- 新增 pkg/errors 包，统一错误处理
- 拆分 captcha 包，图片识别移至 service/recognizer
- 清理 models 包，只保留数据结构定义
- 消除 grpc/handler.go 中的重复代码
- 简化 main.go，使用 slog 和 context
- 配置支持单例模式和结构化配置
- 使用 any 替代 interface{}
- 使用 sync.Map 替代 map + RWMutex

config/config.go

@@ -1,27 +1,101 @@
 package config
 
 import (
+	"log/slog"
 	"os"
+	"strconv"
+	"sync"
+	"time"
 )
 
-// 配置变量
+type Config struct {
+	BaseURL    string
+	Username   string
+	Password   string
+	Semester   string
+	TWFID      string
+	Recognizer RecognizerConfig
+}
+
+type RecognizerConfig struct {
+	APIURL  string
+	APIKey  string
+	Model   string
+	Timeout time.Duration
+}
+
 var (
-	BaseURL  = getEnv("JWTS_BASE_URL", "http://jwts.hitwh.edu.cn")
-	Username = getEnv("JWTS_USERNAME", "")
-	Password = getEnv("JWTS_PASSWORD", "")
-	Semester = getEnv("JWTS_SEMESTER", "2025-20262")
-	TWFID    = getEnv("JWTS_TWFID", "")
-
-	RecognizerAPIURL = getEnv("RECOGNIZER_API_URL", "https://api.littlelan.cn/v1/chat/completions")
-	RecognizerAPIKey = getEnv("RECOGNIZER_API_KEY", "")
-	RecognizerModel  = getEnv("RECOGNIZER_MODEL", "qwen3.5-plus")
+	cfg     *Config
+	cfgOnce sync.Once
 )
 
-// getEnv 从环境变量获取配置，提供默认值
+func Load() *Config {
+	cfgOnce.Do(func() {
+		cfg = &Config{
+			BaseURL:  getEnv("JWTS_BASE_URL", "http://jwts.hitwh.edu.cn"),
+			Username: getEnv("JWTS_USERNAME", ""),
+			Password: getEnv("JWTS_PASSWORD", ""),
+			Semester: getEnv("JWTS_SEMESTER", "2025-20262"),
+			TWFID:    getEnv("JWTS_TWFID", ""),
+			Recognizer: RecognizerConfig{
+				APIURL:  getEnv("RECOGNIZER_API_URL", "https://api.littlelan.cn/v1/chat/completions"),
+				APIKey:  getEnv("RECOGNIZER_API_KEY", ""),
+				Model:   getEnv("RECOGNIZER_MODEL", "qwen3.5-plus"),
+				Timeout: getEnvDuration("RECOGNIZER_TIMEOUT", 120*time.Second),
+			},
+		}
+
+		if cfg.Recognizer.APIKey == "" {
+			slog.Warn("RECOGNIZER_API_KEY not set, image recognition will not work")
+		}
+	})
+	return cfg
+}
+
+func Get() *Config {
+	if cfg == nil {
+		return Load()
+	}
+	return cfg
+}
+
 func getEnv(key, defaultValue string) string {
-	value := os.Getenv(key)
-	if value == "" {
+	val := os.Getenv(key)
+	if val == "" {
 		return defaultValue
 	}
-	return value
+	return val
 }
+
+func getEnvInt(key string, defaultValue int) int {
+	val := os.Getenv(key)
+	if val == "" {
+		return defaultValue
+	}
+	if i, err := strconv.Atoi(val); err == nil {
+		return i
+	}
+	return defaultValue
+}
+
+func getEnvDuration(key string, defaultValue time.Duration) time.Duration {
+	val := os.Getenv(key)
+	if val == "" {
+		return defaultValue
+	}
+	if d, err := time.ParseDuration(val); err == nil {
+		return d
+	}
+	return defaultValue
+}
+
+var (
+	BaseURL          = Get().BaseURL
+	Username         = Get().Username
+	Password         = Get().Password
+	Semester         = Get().Semester
+	TWFID            = Get().TWFID
+	RecognizerAPIURL = Get().Recognizer.APIURL
+	RecognizerAPIKey = Get().Recognizer.APIKey
+	RecognizerModel  = Get().Recognizer.Model
+)