Add file-backed environment secrets

internal/config/load.go

@@ -35,6 +35,10 @@ func Load(opts LoadOptions) (Config, error) {
 		cfg.WeatherAPI.Timezone = opts.Timezone
 	}
 
+	if err := loadSecrets(cfg.Secrets); err != nil {
+		return Config{}, err
+	}
+
 	if err := Validate(cfg); err != nil {
 		return Config{}, err
 	}