feat: implement audit trail alignment (soft delete & permission audit)

- Task Soft Delete:
  - Add is_deleted, deleted_at, deleted_by fields to Task model
  - Convert DELETE to soft delete with cascade to subtasks
  - Add include_deleted query param (admin only)
  - Add POST /api/tasks/{id}/restore endpoint
  - Exclude deleted tasks from subtask_count

- Permission Change Audit:
  - Add user.role_change event (high sensitivity)
  - Add user.admin_change event (critical, triggers alert)
  - Add PATCH /api/users/{id}/admin endpoint
  - Add role.permission_change event type

- Append-Only Enforcement:
  - Add DB triggers for audit_logs immutability (manual for production)
  - Migration 008 with graceful trigger failure handling

- Tests: 11 new soft delete tests (153 total passing)
- OpenSpec: fix-audit-trail archived, fix-realtime-notifications & fix-weekly-report proposals added

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

openspec/changes/fix-weekly-report/tasks.md

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+## Phase 1: Backend Report Enhancement
+
+### 1.1 ReportService 擴充
+- [ ] 1.1.1 移除 completed_tasks/overdue_tasks 的 5 筆限制
+- [ ] 1.1.2 新增 in_progress_tasks 完整清單
+- [ ] 1.1.3 新增 blocked_tasks 查詢與清單
+- [ ] 1.1.4 新增 next_week_tasks 查詢與清單
+- [ ] 1.1.5 擴充 summary 包含 blocked_count 與 next_week_count
+
+### 1.2 任務明細欄位
+- [ ] 1.2.1 completed_tasks 加入 completed_at, assignee_name
+- [ ] 1.2.2 in_progress_tasks 加入 assignee_name, due_date
+- [ ] 1.2.3 overdue_tasks 加入 days_overdue 計算
+- [ ] 1.2.4 blocked_tasks 加入 blocker_reason, blocked_since
+- [ ] 1.2.5 next_week_tasks 加入 due_date, assignee_name
+
+### 1.3 Testing - Phase 1
+- [ ] 1.3.1 週報內容結構測試
+- [ ] 1.3.2 阻礙任務查詢測試
+- [ ] 1.3.3 下週預計任務測試
+
+## Phase 2: Frontend Display
+
+### 2.1 WeeklyReportPreview 更新
+- [ ] 2.1.1 新增 BlockedTasksSection 元件
+- [ ] 2.1.2 新增 NextWeekTasksSection 元件
+- [ ] 2.1.3 更新 CompletedTasksSection 顯示完整清單
+- [ ] 2.1.4 更新 InProgressTasksSection 顯示完整清單
+- [ ] 2.1.5 更新 OverdueTasksSection 顯示 days_overdue
+
+### 2.2 UI 改善
+- [ ] 2.2.1 可摺疊區塊設計
+- [ ] 2.2.2 任務項目樣式統一
+- [ ] 2.2.3 逾期/阻礙 highlight 樣式
+
+### 2.3 Testing - Phase 2
+- [ ] 2.3.1 前端週報顯示測試
+- [ ] 2.3.2 空清單狀態測試