修复：埋点接线与三处偏差（sessionId/eventId/设备信息）

- 生产接线修复：app.dart 组装时传 analytics 实例给 ApiAuthRepository（_buildRepository），修复 M1 遗留的「生产环境 _analytics 恒为 null、挂接点空转」问题
- sessionId 生命周期：新建 SessionTracker (WidgetsBindingObserver)，冷启动生成 UUIDv7、后台超 30 分钟换新、未超阈值沿用原值，不再每事件随机生成
- eventId 改 UUIDv7：对齐 13 号规范（uuid 包已在依赖，直接用 v7()），保留插入时间局部性
- appVersion 动态注入：package_info_plus（新增依赖）异步读取后 setAppVersion，不再硬编码 '1.0.0+1'
- osVersion 动态读取：Platform.operatingSystemVersion 正则提取主版本（如 android-14），不再硬编码
- 队列顺手加固：上传失败批次重回队首而非整批丢弃（一行级缓解，分段持久化属 M2 第二波）

测试新增 9 例：session_tracker_test（5 例：冷启动/短后台/长后台/级联状态/连续幂等），analytics_service_test 补强 4 例（UUIDv7/sessionId 不再逐事件生成/appVersion 可注入/失败重回队列）。

验收对照（06 号报告 §5.1 六条）：1✓ SessionTracker 新建、2✓ 三条语义、3✓ 同会话 sessionId 一致、4✓ sessionId 为 UUID 不持久化、5✓ 单测 3 例（实际 5 例）、6✓ 真机脚本（开发者手测）。

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

test/analytics/session_tracker_test.dart

@@ -0,0 +1,77 @@
+import 'package:flutter/widgets.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:patbond_flutter/analytics/session_tracker.dart';
+
+void main() {
+  final uuidV7 = RegExp(
+    r'^[0-9a-f]{8}-[0-9a-f]{4}-7[0-9a-f]{3}-[0-9a-f]{4}-[0-9a-f]{12}$',
+  );
+
+  group('SessionTracker', () {
+    test('冷启动生成 UUIDv7 格式的 sessionId', () {
+      final tracker = SessionTracker();
+      expect(tracker.sessionId, matches(uuidV7));
+    });
+
+    test('短后台（≤30 分钟）resume 后沿用原 sessionId', () {
+      var clock = DateTime.utc(2026, 9, 7, 10);
+      final tracker = SessionTracker(now: () => clock);
+      final original = tracker.sessionId;
+
+      tracker.didChangeAppLifecycleState(AppLifecycleState.paused);
+      clock = clock.add(const Duration(minutes: 30));
+      tracker.didChangeAppLifecycleState(AppLifecycleState.resumed);
+
+      expect(tracker.sessionId, original);
+    });
+
+    test('长后台（>30 分钟）resume 后生成新 sessionId', () {
+      var clock = DateTime.utc(2026, 9, 7, 10);
+      final tracker = SessionTracker(now: () => clock);
+      final original = tracker.sessionId;
+
+      tracker.didChangeAppLifecycleState(AppLifecycleState.paused);
+      clock = clock.add(const Duration(minutes: 31));
+      tracker.didChangeAppLifecycleState(AppLifecycleState.resumed);
+
+      expect(tracker.sessionId, isNot(original));
+      expect(tracker.sessionId, matches(uuidV7));
+    });
+
+    test('真实生命周期级联下退后台时刻不被 inactive 覆盖', () {
+      // 前台恢复时状态机级联 paused → hidden → inactive → resumed，
+      // 若 inactive 覆盖记时，31 分钟长后台会被误判为 0 分钟。
+      var clock = DateTime.utc(2026, 9, 7, 10);
+      final tracker = SessionTracker(now: () => clock);
+      final original = tracker.sessionId;
+
+      tracker.didChangeAppLifecycleState(AppLifecycleState.inactive);
+      tracker.didChangeAppLifecycleState(AppLifecycleState.hidden);
+      tracker.didChangeAppLifecycleState(AppLifecycleState.paused);
+      clock = clock.add(const Duration(minutes: 31));
+      tracker.didChangeAppLifecycleState(AppLifecycleState.hidden);
+      tracker.didChangeAppLifecycleState(AppLifecycleState.inactive);
+      tracker.didChangeAppLifecycleState(AppLifecycleState.resumed);
+
+      expect(tracker.sessionId, isNot(original));
+    });
+
+    test('连续多次短后台幂等，仅超阈值才换新', () {
+      var clock = DateTime.utc(2026, 9, 7, 10);
+      final tracker = SessionTracker(now: () => clock);
+      final original = tracker.sessionId;
+
+      for (var i = 0; i < 3; i++) {
+        tracker.didChangeAppLifecycleState(AppLifecycleState.paused);
+        clock = clock.add(const Duration(minutes: 10));
+        tracker.didChangeAppLifecycleState(AppLifecycleState.resumed);
+        expect(tracker.sessionId, original);
+      }
+
+      tracker.didChangeAppLifecycleState(AppLifecycleState.paused);
+      clock = clock.add(const Duration(minutes: 35));
+      tracker.didChangeAppLifecycleState(AppLifecycleState.resumed);
+      expect(tracker.sessionId, isNot(original));
+    });
+  });
+}