feat(task): adopt JPA feature boundaries

docs/tests/unit/task-persistence-structure.md

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+# Test Evidence: Task feature persistence structure
+
+- **Test type:** Unit
+- **Requirement IDs:** `TSK-001`–`TSK-005`, `TSK-007`, `TSK-011`, `TSK-012`
+- **Scenario IDs:** `I1-TSK-01`–`I1-TSK-04`
+- **Test class/method:** `com.lab.labtimesheet.feature.task.repository.TaskPersistenceStructureTest#taskPersistenceUsesJpaEntitiesAndSpringDataRepositories`
+- **Implementation commit:** `pending`
+
+## Protected behavior
+
+Task persistence uses JPA entities in `feature.task.model.entity` and Spring Data repositories in `feature.task.repository`. Status/comment mutation lookup is protected by `PESSIMISTIC_WRITE`. This prevents a regression to business-level JDBC access, unlocked mutation reads, or a global layer package.
+
+## Test method
+
+Four focused tests load the production `Task` and `TaskComment` classes, verify their `@Entity` annotations, verify that both production repository interfaces extend `JpaRepository`, reject direct JDBC imports in Task business code, and inspect the locked lookup's `@Lock(PESSIMISTIC_WRITE)` annotation.
+
+## Hand-derived expected result
+
+Exactly two Task-owned persisted aggregates are required for Iteration 1: `Task` and append-only `TaskComment`. Each must be a JPA entity, and each repository must be a Spring Data JPA repository under the Task feature package.
+
+## RED
+
+**Command**
+
+```text
+export JAVA_HOME=/opt/homebrew/opt/openjdk@25
+export PATH="$JAVA_HOME/bin:$PATH"
+./mvnw -Dtest=TaskPersistenceStructureTest test
+```
+
+**Observed result**
+
+```text
+[ERROR] TaskPersistenceStructureTest.java:[5,54] package com.lab.labtimesheet.feature.task.model.entity does not exist
+[ERROR] TaskPersistenceStructureTest.java:[6,54] package com.lab.labtimesheet.feature.task.model.entity does not exist
+[INFO] BUILD FAILURE
+```
+
+The final feature-first package contract did not yet exist.
+
+After that package move reached GREEN, the business-persistence boundary was tightened with a second test and separately observed RED:
+
+```text
+[ERROR] Tests run: 3, Failures: 2, Errors: 0, Skipped: 0
+Expecting [org.springframework.jdbc.core.simple.JdbcClient]
+to contain [TaskRepository, TaskCommentRepository]
+Expecting empty but was: [src/main/java/com/lab/labtimesheet/feature/task/service/TaskService.java]
+[INFO] BUILD FAILURE
+```
+
+The second failure proves that `TaskService` still depended on direct JDBC instead of the two Task-owned Spring Data repositories.
+
+## GREEN
+
+**Command**
+
+```text
+export JAVA_HOME=/opt/homebrew/opt/openjdk@25
+export PATH="$JAVA_HOME/bin:$PATH"
+./mvnw -Dtest=TaskPersistenceStructureTest test
+```
+
+**Observed result**
+
+```text
+[INFO] Tests run: 4, Failures: 0, Errors: 0, Skipped: 0
+[INFO] BUILD SUCCESS
+```
+
+## Affected suite
+
+**Command and result**
+
+```text
+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=TaskPersistenceStructureTest,TaskDomainRulesTest,TaskControllerTest,TaskQueryServiceTest,TaskDashboardServiceTest,TaskMutationBoundaryTest,TaskCreationIntegrationTest test
+
+[INFO] Tests run: 51, Failures: 0, Errors: 0, Skipped: 0
+[INFO] BUILD SUCCESS
+```
+
+The suite ran with approved escalation for PostgreSQL 18.4 Testcontainers and Mockito Java 25 self-attach.
+
+## External-test boundaries
+
+This structure test does not prove persistence mappings against PostgreSQL, transactional authorization, cross-feature service contracts, or rendered behavior. Those remain protected by the Task integration and web evidence after the dependency foundations are merged.