Session-end timer runs on java.util.Timer

Audit finding **B2 — actual bug, MEDIUM**.

`LifecycleWatcher` schedules session end with `java.util.Timer` (`new Timer(true)` / `scheduleEndSession`, `sentry-android-core/src/main/java/io/sentry/android/core/LifecycleWatcher.java:106-122`), sharing B1's mechanics:

* Device sleeps within the 30s background window → session ends only at wake; `Session.end()` stamps wake time → inflated session durations in release health. Replay `stop()` and `ContinuousProfiler.close(false)` also run hours late.
* The foreground check `lastUpdatedSession + sessionIntervalMillis <= now` is a wall-clock interval → a clock step causes spurious or missed session rotation.

Source: [JAVA-557]() §B2.