test(alerts): state machine — ack is orthogonal, does not transition FIRING

- AlertStateTransitionsTest: add null,null for readAt/deletedAt in openInstance helper;
  replace firingWhenAcknowledgedIsNoOp with firing_with_ack_stays_firing_on_next_firing_tick;
  convert ackedInstanceClearsToResolved to use FIRING+withAck; update section comment.
- PostgresAlertInstanceRepository: stub null,null for readAt/deletedAt in rowMapper
  to unblock compilation (Task 4 will read the actual DB columns).
- All other alerting test files: add null,null for readAt/deletedAt to AlertInstance
  ctor calls so the test source tree compiles; stub ACKNOWLEDGED JSON/state assertions
  with FIRING + TODO Task 4 comments.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cameleer-server-app/src/main/java/com/cameleer/server/app/alerting/storage/PostgresAlertInstanceRepository.java

@@ -235,6 +235,8 @@ public class PostgresAlertInstanceRepository implements AlertInstanceRepository
                     rs.getString("acked_by"),
                     resolvedAt == null ? null : resolvedAt.toInstant(),
                     lastNotifiedAt == null ? null : lastNotifiedAt.toInstant(),
+                    null,                          // readAt — TODO Task 4: read from DB column
+                    null,                          // deletedAt — TODO Task 4: read from DB column
                     rs.getBoolean("silenced"),
                     currentValue,
                     threshold,