feat(v0.1.7): port iperf3 configurable + iperf3 docker sur port 5202

- config.toml: nouveau champ [server] iperf3_port (défaut 5201)
- network_info: iperf3 -p <port> utilise le port configuré
- docker-compose: iperf3 exposé sur 5202 (5201 occupé par linux_benchtools)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

agent/src/config.rs

@@ -13,8 +13,12 @@ pub struct Config {
 pub struct ServerConfig {
     pub ip: String,
     pub port: u16,
+    #[serde(default = "default_iperf3_port")]
+    pub iperf3_port: u16,
 }
 
+fn default_iperf3_port() -> u16 { 5201 }
+
 #[derive(Deserialize, Debug, Clone, Default)]
 pub struct ProtocolsConfig {
     #[serde(default)]