fix(attendance): preserve frozen attendance boundaries

docs/tests/unit/attendance-policy.md

@@ -4,7 +4,7 @@
 - **Requirement IDs:** `ATT-001`, `ATT-002`, `ATT-003`, `ATT-004`
 - **Scenario IDs:** `AC-ATT-001`
 - **Test class/method:** `com.lab.labtimesheet.feature.attendance.model.AttendancePolicyTest`
-- **Implementation commit:** `pending (committed with this evidence)`
+- **Implementation commit:** `71901d1670f633a1b594bdce3348efebe73fc175`
 
 ## Protected behavior
 
@@ -66,7 +66,7 @@ Process exited 0.
 
 ```text
 ./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.
 ```