feat: 添加配置加载和日志配置支持

- 新增 LogConfig 结构体，支持 9 个日志配置字段（level, encoding, output_stdout, file_path, max_size, max_backups, max_age, compress, gorm_level）

- Config 结构体新增 Log 字段，支持 YAML 解析

- output_stdout 使用 *bool 指针类型，nil 默认为 true

- 更新 config.example.yaml 添加完整 log 配置段

- 新增 TDD 测试：日志配置解析、向后兼容、字段完整性

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

internal/config/config.go

@@ -0,0 +1,51 @@
+package config
+
+import (
+	"fmt"
+	"os"
+
+	"gopkg.in/yaml.v3"
+)
+
+// LogConfig holds logging configuration values.
+type LogConfig struct {
+	Level        string `yaml:"level"`         // debug, info, warn, error (default: info)
+	Encoding     string `yaml:"encoding"`      // json, console (default: json)
+	OutputStdout *bool  `yaml:"output_stdout"` // 输出到终端 (default: true)
+	FilePath     string `yaml:"file_path"`     // log file path (for rotation)
+	MaxSize      int    `yaml:"max_size"`      // MB per file (default: 100)
+	MaxBackups   int    `yaml:"max_backups"`   // retained files (default: 5)
+	MaxAge       int    `yaml:"max_age"`       // days to retain (default: 30)
+	Compress     bool   `yaml:"compress"`      // gzip old files (default: true)
+	GormLevel    string `yaml:"gorm_level"`    // GORM SQL log level (default: warn)
+}
+
+// Config holds all application configuration values.
+type Config struct {
+	ServerPort      string    `yaml:"server_port"`
+	SlurmAPIURL     string    `yaml:"slurm_api_url"`
+	SlurmUserName   string    `yaml:"slurm_user_name"`
+	SlurmJWTKeyPath string    `yaml:"slurm_jwt_key_path"`
+	MySQLDSN        string    `yaml:"mysql_dsn"`
+	Log             LogConfig `yaml:"log"`
+}
+
+// Load reads a YAML configuration file and returns a parsed Config.
+// If path is empty, it defaults to "./config.yaml".
+func Load(path string) (*Config, error) {
+	if path == "" {
+		path = "./config.yaml"
+	}
+
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("read config file %s: %w", path, err)
+	}
+
+	var cfg Config
+	if err := yaml.Unmarshal(data, &cfg); err != nil {
+		return nil, fmt.Errorf("parse config file %s: %w", path, err)
+	}
+
+	return &cfg, nil
+}