Update config struct tags from YAML to JSON

- Changed struct tags in `cmd/app/config.go` from `yaml` to `json`
- Maintains existing configuration structure while switching serialization format

cmd/app/config.go

@@ -16,28 +16,28 @@ const (
 )
 
 type Config struct {
-	DBConfig      *DBConfig      `yaml:"db_config"`
-	RegionConfigs []RegionConfig `yaml:"region_configs"`
-	Debug         bool           `yaml:"debug"`
-	GatewayUrl    string         `yaml:"gateway_url"`
+	DBConfig      *DBConfig      `json:"db_config"`
+	RegionConfigs []RegionConfig `json:"region_configs"`
+	Debug         bool           `json:"debug"`
+	GatewayUrl    string         `json:"gateway_url"`
 }
 
 type DBConfig struct {
-	User     string `yaml:"user"`
-	Password string `yaml:"password"`
-	Host     string `yaml:"host"`
-	Port     string `yaml:"port"`
-	Database string `yaml:"database"`
+	User     string `json:"user"`
+	Password string `json:"password"`
+	Host     string `json:"host"`
+	Port     string `json:"port"`
+	Database string `json:"database"`
 }
 
 type RegionConfig struct {
-	RegionCode     string `yaml:"region_code"`
-	ApiServer      string `yaml:"api_server"`
-	CAData         string `yaml:"ca_data"`
-	Token          string `yaml:"token"`
-	ClientCertData string `yaml:"client_cert_data"`
-	ClientKeyData  string `yaml:"client_key_data"`
-	Insecure       bool   `yaml:"insecure"`
+	RegionCode     string `json:"region_code"`
+	ApiServer      string `json:"api_server"`
+	CAData         string `json:"ca_data"`
+	Token          string `json:"token"`
+	ClientCertData string `json:"client_cert_data"`
+	ClientKeyData  string `json:"client_key_data"`
+	Insecure       bool   `json:"insecure"`
 }
 
 func LoadConfig() *Config {