feat(stats): #10 第②层 —— 统计页按设备过滤(per-device 本地日曲线)

镜像账户级时区曲线到「按设备」:
- migration 000018 `usage_device_hourly`(每设备 UTC 小时桶,稀疏)。
- ReportUsage deviceID>0 时加 AccumulateDeviceHourly;NodeStore 接口+impl+mock。
- usage.Store.DeviceHourlyRange(JOIN devices 校验归属+解析 uuid→id);UsageCurve
  增 deviceUUID 形参:空=账户级,非空=该设备本地日曲线(分桶逻辑复用)。
- /v1/usage?device=<uuid>;客户端 account_api.usage(device)、usageProvider key 改
  记录 (days,device)、stats_page 接 statsDeviceProvider → 选设备即重取该设备曲线。
测试:per-device 曲线隔离+归属校验(A的设备不进B)、UsageCurve(deviceUUID)、
migration v18、客户端 widget(选设备→/v1/usage 带 device=)。全量 go/flutter 绿。

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

client/test/golden/tablet_pages_golden_test.dart

@@ -115,7 +115,7 @@ Future<void> _shoot(
         localeProvider.overrideWith((ref) => lang),
         nodesProvider.overrideWith(_FakeNodesNotifier.new),
         meProvider.overrideWith(_FakeMeNotifier.new),
-        usageProvider(30).overrideWith((ref) async => _demoUsage),
+        usageProvider((days: 30, device: null)).overrideWith((ref) async => _demoUsage),
         deviceUsageProvider(30).overrideWith((ref) async => _demoDeviceUsage),
       ],
       child: MaterialApp(

client/test/widget/stats_device_filter_test.dart

@@ -0,0 +1,87 @@
+// stats_device_filter_test.dart — #10②:统计页选设备 → /v1/usage 带 device 参数。
+import 'dart:convert';
+
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:http/http.dart' as http;
+import 'package:http/testing.dart';
+import 'package:pangolin_vpn/l10n/strings_zh.dart';
+import 'package:pangolin_vpn/pangolin_theme.dart';
+import 'package:pangolin_vpn/screens/stats_page.dart';
+import 'package:pangolin_vpn/services/api_client.dart';
+import 'package:pangolin_vpn/services/token_store.dart';
+import 'package:pangolin_vpn/state/account_providers.dart';
+import 'package:pangolin_vpn/state/auth_provider.dart';
+
+import '../helpers/harness.dart';
+
+class _LoggedIn implements TokenStore {
+  const _LoggedIn();
+  @override
+  Future<String?> loadAccessToken() async => 'tok';
+  @override
+  Future<String?> loadRefreshToken() async => null;
+  @override
+  Future<void> saveTokens({required String access, required String refresh}) async {}
+  @override
+  Future<void> clear() async {}
+  @override
+  Future<void> markOnboarded() async {}
+  @override
+  Future<bool> isOnboarded() async => true;
+  @override
+  Future<void> saveLastEmail(String email) async {}
+  @override
+  Future<String?> loadLastEmail() async => null;
+}
+
+void main() {
+  setUpAll(disableGoogleFontsFetching);
+  const t = StringsZh();
+
+  testWidgets('选设备 → /v1/usage 带 device=<uuid>', (tester) async {
+    await tester.binding.setSurfaceSize(const Size(900, 1200));
+    addTearDown(() => tester.binding.setSurfaceSize(null));
+
+    final usageDeviceParams = <String?>[];
+    final mock = MockClient((req) async {
+      final p = req.url.path;
+      if (p == '/v1/me') {
+        return http.Response(jsonEncode({'email': 'u@e', 'plan': 'free', 'devices_used': 1, 'devices_max': 5}), 200);
+      }
+      if (p == '/v1/usage') {
+        usageDeviceParams.add(req.url.queryParameters['device']);
+        return http.Response(jsonEncode({'points': []}), 200);
+      }
+      if (p == '/v1/usage/devices') {
+        return http.Response(jsonEncode({'devices': [
+          {'uuid': 'dev-1', 'name': 'iPhone', 'platform': 'ios', 'bytes_up': 10, 'bytes_down': 20, 'minutes_used': 3},
+        ]}), 200);
+      }
+      return http.Response('{}', 200);
+    });
+
+    await tester.pumpWidget(ProviderScope(
+      overrides: [
+        tokenStoreProvider.overrideWithValue(const _LoggedIn()),
+        apiClientProvider.overrideWithValue(ApiClient(
+          baseUrl: 'http://test.local', getToken: () => 'tok', refresh: () async => false, client: mock,
+        )),
+      ],
+      child: MaterialApp(theme: PangolinTheme.light, home: const Scaffold(body: StatsPage(isWide: true))),
+    ));
+    await tester.pumpAndSettle();
+
+    // 初次:账户级,不带 device。
+    expect(usageDeviceParams.contains(null), isTrue, reason: '首拉应不带 device: $usageDeviceParams');
+
+    // 打开下拉,选 iPhone。
+    await tester.tap(find.byType(PopupMenuButton<String>));
+    await tester.pumpAndSettle();
+    await tester.tap(find.text('iPhone').last);
+    await tester.pumpAndSettle();
+
+    expect(usageDeviceParams.contains('dev-1'), isTrue, reason: '选设备后应带 device=dev-1: $usageDeviceParams');
+  });
+}