feat: métriques réseau+hardware serveur+dashboard + API /agents/{id} + iperf3

Serveur:
- Modèles Go: NetworkInterface, HardwareInfo dans Agent + AgentMetrics
- DB: migrations network_info_json + hardware_info_json dans agents
- UpsertAgent: stocke les données lentes si présentes dans le payload
- GetAgents: désérialise network_info_json + hardware_info_json
- GET /api/agents/{id}: endpoint single agent
- docker-compose: service iperf3 (port 5201)

Dashboard:
- Popup détail: section RÉSEAU (tableau interfaces: type, vitesse, MAC, WoL, iperf3)
- Popup détail: section HARDWARE (carte mère, CPU, RAM slots/type/vitesse)
- CSS: .net-table/.net-row pour le tableau réseau
- Font-size global appliqué sur html root (au lieu de body)

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

server/db/db.go

@@ -68,6 +68,8 @@ func (d *DB) migrate() error {
 	_, _ = d.conn.Exec(`ALTER TABLE metrics ADD COLUMN smart_hours   INTEGER`)
 	_, _ = d.conn.Exec(`ALTER TABLE metrics ADD COLUMN smart_wear    INTEGER`)
 	_, _ = d.conn.Exec(`ALTER TABLE metrics ADD COLUMN smart_json    TEXT`)
+	_, _ = d.conn.Exec(`ALTER TABLE agents ADD COLUMN network_info_json TEXT`)
+	_, _ = d.conn.Exec(`ALTER TABLE agents ADD COLUMN hardware_info_json TEXT`)
 	return nil
 }
 
@@ -75,13 +77,27 @@ func (d *DB) Close() { _ = d.conn.Close() }
 
 func (d *DB) UpsertAgent(m *models.AgentMetrics) error {
 	ts := time.Now().Unix()
+	var netJSON, hwJSON interface{}
+	if len(m.NetworkInfo) > 0 {
+		if b, err := json.Marshal(m.NetworkInfo); err == nil {
+			netJSON = string(b)
+		}
+	}
+	if m.HardwareInfo != nil {
+		if b, err := json.Marshal(m.HardwareInfo); err == nil {
+			hwJSON = string(b)
+		}
+	}
 	_, err := d.conn.Exec(`
-		INSERT INTO agents (id, hostname, ip, status, last_seen, version)
-		VALUES (?, ?, ?, ?, ?, ?)
+		INSERT INTO agents (id, hostname, ip, status, last_seen, version,
+			network_info_json, hardware_info_json)
+		VALUES (?, ?, ?, ?, ?, ?, ?, ?)
 		ON CONFLICT(id) DO UPDATE SET
 			ip=excluded.ip, status=excluded.status, last_seen=excluded.last_seen,
-			version=CASE WHEN excluded.version != '' THEN excluded.version ELSE version END`,
-		m.Hostname, m.Hostname, m.IP, m.Status, ts, m.Version)
+			version=CASE WHEN excluded.version != '' THEN excluded.version ELSE version END,
+			network_info_json=CASE WHEN excluded.network_info_json IS NOT NULL THEN excluded.network_info_json ELSE network_info_json END,
+			hardware_info_json=CASE WHEN excluded.hardware_info_json IS NOT NULL THEN excluded.hardware_info_json ELSE hardware_info_json END`,
+		m.Hostname, m.Hostname, m.IP, m.Status, ts, m.Version, netJSON, hwJSON)
 	return err
 }
 
@@ -109,7 +125,8 @@ func (d *DB) InsertMetrics(m *models.AgentMetrics) error {
 }
 
 func (d *DB) GetAgents() ([]models.Agent, error) {
-	rows, err := d.conn.Query(`SELECT id, hostname, ip, status, last_seen, version FROM agents`)
+	rows, err := d.conn.Query(`SELECT id, hostname, ip, status, last_seen, version,
+		network_info_json, hardware_info_json FROM agents`)
 	if err != nil {
 		return nil, err
 	}
@@ -117,9 +134,17 @@ func (d *DB) GetAgents() ([]models.Agent, error) {
 	var agents []models.Agent
 	for rows.Next() {
 		var a models.Agent
-		if err := rows.Scan(&a.ID, &a.Hostname, &a.IP, &a.Status, &a.LastSeen, &a.Version); err != nil {
+		var netJSON, hwJSON *string
+		if err := rows.Scan(&a.ID, &a.Hostname, &a.IP, &a.Status, &a.LastSeen, &a.Version,
+			&netJSON, &hwJSON); err != nil {
 			return nil, err
 		}
+		if netJSON != nil {
+			_ = json.Unmarshal([]byte(*netJSON), &a.NetworkInfo)
+		}
+		if hwJSON != nil {
+			_ = json.Unmarshal([]byte(*hwJSON), &a.HardwareInfo)
+		}
 		agents = append(agents, a)
 	}
 	if err := rows.Err(); err != nil {