ax(mining): rename cfg→configuration in LoadMinersConfig

AX principle 1: predictable names over short names.
`cfg` requires mapping overhead; `configuration` is unambiguous.

Co-Authored-By: Charon <charon@lethean.io>

pkg/mining/config_manager.go

@@ -69,17 +69,17 @@ func LoadMinersConfig() (*MinersConfig, error) {
 		return nil, fmt.Errorf("failed to read miners config file: %w", err)
 	}
 
-	var cfg MinersConfig
-	if err := json.Unmarshal(data, &cfg); err != nil {
+	var configuration MinersConfig
+	if err := json.Unmarshal(data, &configuration); err != nil {
 		return nil, fmt.Errorf("failed to unmarshal miners config: %w", err)
 	}
 
 	// Apply default database config if not set (for backwards compatibility)
-	if cfg.Database.RetentionDays == 0 {
-		cfg.Database = defaultDatabaseConfig()
+	if configuration.Database.RetentionDays == 0 {
+		configuration.Database = defaultDatabaseConfig()
 	}
 
-	return &cfg, nil
+	return &configuration, nil
 }
 
 // SaveMinersConfig saves the miners configuration to the file system.