feat(config): add WorkDirBase for application job working directory

Add WorkDirBase config field for auto-generated job working directories. Pattern: {base}/{app_name}/{timestamp}_{random}/

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

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

internal/config/config.go

@@ -27,6 +27,7 @@ type Config struct {
 	SlurmUserName   string    `yaml:"slurm_user_name"`
 	SlurmJWTKeyPath string    `yaml:"slurm_jwt_key_path"`
 	MySQLDSN        string    `yaml:"mysql_dsn"`
+	WorkDirBase     string    `yaml:"work_dir_base"` // base directory for job work dirs
 	Log             LogConfig `yaml:"log"`
 }