feat(#402): config-profile schema + model

Typed model for importable device config profiles (feature #136): WifiConfig,
BrokerConfig (6 slots), region/status-interval, and a ConfigProfile container.
All fields nullable so apply engines write only the keys a profile sets.

Key names + wire encoding mirror the firmware ConfigSchema (transport/auth as
string names, wifi.pwd write-only). ConfigKeys centralizes the key strings so
the parser (#403) and per-device apply engines never hard-code them.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

lib/models/config_profile.dart

@@ -0,0 +1,172 @@
+/// Importable device config-profile model (#402, feature #136).
+///
+/// A profile is a portable set of config values a user applies to a device
+/// (observer #139, repeater #137, companion #138) instead of baked defaults.
+/// This file defines only the schema and typed model — parsing (#403) and the
+/// per-device apply engines live elsewhere.
+///
+/// Every field is nullable: a profile carries only the keys it wants to set, so
+/// the apply engines can write field-at-a-time and leave everything else alone.
+///
+/// Key names and the wire encoding mirror the firmware config schema
+/// (`meshcore-firmware/.../wifi_observer/ConfigSchema.h`). transport and
+/// auth_type travel as their string names, not the NVS ordinals.
+library;
+
+/// Bumped when the on-disk/YAML shape changes incompatibly. The parser (#403)
+/// rejects a profile whose declared version it does not understand.
+const int kConfigProfileSchemaVersion = 1;
+
+/// Number of broker slots the firmware exposes (`mqtt_b0`..`mqtt_b5`).
+const int kMaxBrokerSlots = 6;
+
+/// MQTT transport — wire value is the name (`tcp`/`tls`/`wss`), not the ordinal.
+enum MqttTransport {
+  tcp,
+  tls,
+  wss;
+
+  String get wire => name;
+
+  static MqttTransport? fromWire(String? v) {
+    if (v == null) return null;
+    for (final t in values) {
+      if (t.name == v.toLowerCase()) return t;
+    }
+    return null;
+  }
+}
+
+/// MQTT auth type — wire value is the name (`none`/`basic`/`jwt`).
+enum MqttAuthType {
+  none,
+  basic,
+  jwt;
+
+  String get wire => name;
+
+  static MqttAuthType? fromWire(String? v) {
+    if (v == null) return null;
+    for (final a in values) {
+      if (a.name == v.toLowerCase()) return a;
+    }
+    return null;
+  }
+}
+
+/// WiFi credentials (`wifi.*`). [password] maps to the firmware's `wifi.pwd`
+/// and is write-only on the device (GET returns an error), so a profile can set
+/// it but never round-trips it back.
+class WifiConfig {
+  const WifiConfig({this.ssid, this.password, this.enabled});
+
+  final String? ssid;
+  final String? password;
+  final bool? enabled;
+
+  bool get isEmpty => ssid == null && password == null && enabled == null;
+}
+
+/// One broker slot (`mqtt.broker.<slot>.*`). Sensitive fields ([password],
+/// [jwtToken]) are included so a profile *can* carry them, but sharing a profile
+/// with secrets is a trust concern the import flow must surface (#139 trust note).
+class BrokerConfig {
+  const BrokerConfig({
+    required this.slot,
+    this.enabled,
+    this.url,
+    this.port,
+    this.transport,
+    this.authType,
+    this.username,
+    this.password,
+    this.jwtToken,
+    this.jwtAudience,
+    this.jwtRefresh,
+    this.jwtOwner,
+    this.jwtEmail,
+    this.caCert,
+    this.topicPrefix,
+    this.iataOverride,
+  });
+
+  /// 0-based slot index, `0 <= slot < kMaxBrokerSlots`.
+  final int slot;
+  final bool? enabled;
+  final String? url;
+  final int? port;
+  final MqttTransport? transport;
+  final MqttAuthType? authType;
+  final String? username;
+  final String? password;
+  final String? jwtToken;
+  final String? jwtAudience;
+  final int? jwtRefresh;
+  final String? jwtOwner;
+  final String? jwtEmail;
+  final String? caCert;
+  final String? topicPrefix;
+  final String? iataOverride;
+}
+
+/// A complete importable config profile.
+class ConfigProfile {
+  const ConfigProfile({
+    required this.schemaVersion,
+    this.wifi,
+    this.regionIata,
+    this.statusInterval,
+    this.brokers = const [],
+    this.name,
+  });
+
+  final int schemaVersion;
+  final WifiConfig? wifi;
+
+  /// `mqtt.iata` — the region/IATA code applied globally.
+  final String? regionIata;
+
+  /// `mqtt.status_interval` — seconds between status publishes.
+  final int? statusInterval;
+
+  /// Populated broker slots only (may be sparse; each carries its [BrokerConfig.slot]).
+  final List<BrokerConfig> brokers;
+
+  /// Optional human label for the profile (not applied to the device).
+  final String? name;
+}
+
+/// Firmware config-key names. Callers (parser #403, apply engines) build keys
+/// from these rather than hard-coding strings, so a firmware rename lands in one
+/// place. Broker keys are `mqtt.broker.<slot>.<subkey>`.
+abstract final class ConfigKeys {
+  static const String wifiPrefix = 'wifi.';
+  static const String wifiSsid = 'wifi.ssid';
+  static const String wifiPassword = 'wifi.pwd';
+  static const String wifiEnabled = 'wifi.enabled';
+
+  static const String mqttIata = 'mqtt.iata';
+  static const String mqttStatusInterval = 'mqtt.status_interval';
+
+  static const String brokerPrefix = 'mqtt.broker.';
+
+  // Broker sub-keys, appended after `mqtt.broker.<slot>.`.
+  static const String brokerEnabled = 'enabled';
+  static const String brokerUrl = 'url';
+  static const String brokerPort = 'port';
+  static const String brokerTransport = 'transport';
+  static const String brokerAuthType = 'auth_type';
+  static const String brokerUsername = 'username';
+  static const String brokerPassword = 'password';
+  static const String brokerJwtToken = 'jwt_token';
+  static const String brokerJwtAudience = 'jwt_aud';
+  static const String brokerJwtRefresh = 'jwt_refresh';
+  static const String brokerJwtOwner = 'jwt_owner';
+  static const String brokerJwtEmail = 'jwt_email';
+  static const String brokerCaCert = 'ca_cert';
+  static const String brokerTopicPrefix = 'topic_prefix';
+  static const String brokerIataOverride = 'iata_override';
+
+  /// Full key for a broker sub-key, e.g. `mqtt.broker.2.url`.
+  static String broker(int slot, String subKey) => '$brokerPrefix$slot.$subKey';
+}