fix(attendance): preserve frozen attendance boundaries

docs/tests/integration/attendance-persistence.md

@@ -4,7 +4,7 @@
 - **Requirement IDs:** `ATT-002`, `ATT-005`, `ATT-007`, `ATT-008`, `ATT-010`, `CAL-001`, `CAL-006`, `CAL-007`, `CAL-009`, `AUTH-003`, `RPT-004`
 - **Scenario IDs:** `AC-ATT-003`, `AC-ATT-004`, `AC-CAL-003`, `AC-CAL-004`
 - **Test class/method:** `com.lab.labtimesheet.feature.attendance.service.AttendancePersistenceIntegrationTest`
-- **Implementation commit:** `pending (committed with this evidence)`
+- **Implementation commit:** `8b48e281f7e860af435ae35b16c4edeb139286dc`
 
 ## Protected behavior
 
@@ -87,7 +87,7 @@ export JAVA_HOME=/opt/homebrew/opt/openjdk@25
 export PATH="$JAVA_HOME/bin:$PATH"
 export DOCKER_HOST=unix:///Users/sechmachine/.orbstack/run/docker.sock
 ./mvnw -Dtest='*Attendance*Test' test
-Tests run: 26, Failures: 0, Errors: 0, Skipped: 0
+Tests run: 32, Failures: 0, Errors: 0, Skipped: 0
 BUILD SUCCESS
 Process exited 0.
 ```