fix(attendance): preserve frozen attendance boundaries

docs/tests/unit/attendance-feature-structure.md

@@ -4,7 +4,7 @@
 - **Requirement IDs:** `ARC-005`, `OPS-020`
 - **Scenario IDs:** `I1-ATT-01` through `I1-ATT-05` structural gate
 - **Test class/method:** `com.lab.labtimesheet.architecture.AttendanceLayerStructureTest`
-- **Implementation commit:** `pending (committed with this evidence)`
+- **Implementation commit:** `8b48e281f7e860af435ae35b16c4edeb139286dc`
 
 ## Protected behavior
 
@@ -90,7 +90,7 @@ 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.
 ```