[alerter]bugfix: preserve group alert recovery events

[hutiefang76]

What's changed

Close #4160.

This fixes two group alert lifecycle cases:

• do not let the firing repeat interval suppress pending resolved alerts in a mixed firing group
• recompute the persisted group status from all known member alerts, so one recovered alert does not mark the whole group resolved while another member is still firing

Regression tests cover both the in-memory group reducer path and the database store path.

Verification

• JAVA_HOME=$(/usr/libexec/java_home -v 25 2>/dev/null || /usr/libexec/java_home) ./mvnw -pl hertzbeat-alerter -am test
• git diff --check

[Copilot]

Pull request overview

This PR fixes two alert-group lifecycle edge cases in the alerter pipeline: ensuring recovery (resolved) events are not suppressed by the firing repeat-interval throttle, and ensuring persisted group status reflects the aggregate state of all known member alerts (not just the current push window).

Changes:

• Bypass the group repeat-interval throttle when the group payload includes any resolved member alerts.
• Recompute a group’s persisted status in the DB store layer from all member alert statuses (by fingerprint), and add regression tests for both reducer and store paths.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 3 comments.

File	Description
hertzbeat-alerter/src/main/java/org/apache/hertzbeat/alert/reduce/AlarmGroupReduce.java	Adjusts repeat-throttle behavior so mixed firing groups with resolved members are still dispatched.
hertzbeat-alerter/src/main/java/org/apache/hertzbeat/alert/notice/impl/DbAlertStoreHandlerImpl.java	Recomputes persisted group status from stored member alerts before saving.
hertzbeat-alerter/src/test/java/org/apache/hertzbeat/alert/reduce/AlarmGroupReduceTest.java	Adds a regression test for “resolved bypasses repeat throttle”.
hertzbeat-alerter/src/test/java/org/apache/hertzbeat/alert/notice/impl/DbAlertStoreHandlerImplTest.java	Adds a regression test ensuring group status stays firing when other members still fire.

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[hutiefang76]

I rebased the branch onto the current master and rechecked the three earlier review points on the latest head: missing group rules now use the default repeat interval, resolved groups reload the full persisted member list, and firing groups skip the extra DB lookup. The focused AlarmGroupReduceTest and DbAlertStoreHandlerImplTest suites pass locally (11 tests, 0 failures/errors), with checkstyle passing across the reactor. The old threads are now outdated and resolved; this is ready for maintainer review.