feat(backend): Create Sprint 2 backend Stories and Tasks

Created detailed implementation plans for Sprint 2 backend work:

Story 1: Audit Log Foundation (Phase 1)
- Task 1: Design AuditLog database schema and create migration
- Task 2: Create AuditLog entity and Repository
- Task 3: Implement EF Core SaveChangesInterceptor
- Task 4: Write unit tests for audit logging
- Task 5: Integrate with ProjectManagement Module

Story 2: Audit Log Core Features (Phase 2)
- Task 1: Implement Changed Fields Detection (JSON Diff)
- Task 2: Integrate User Context Tracking
- Task 3: Add Multi-Tenant Isolation
- Task 4: Implement Audit Query API
- Task 5: Write Integration Tests

Story 3: Sprint Management Module
- Task 1: Create Sprint Aggregate Root and Domain Events
- Task 2: Implement Sprint Repository and EF Core Configuration
- Task 3: Create CQRS Commands and Queries
- Task 4: Implement Burndown Chart Calculation
- Task 5: Add SignalR Real-Time Notifications
- Task 6: Write Integration Tests

Total: 3 Stories, 16 Tasks, 24 Story Points (8+8+8)
Estimated Duration: 10-12 days

All tasks include:
- Detailed technical implementation guidance
- Code examples and file paths
- Testing requirements (>= 90% coverage)
- Performance benchmarks (< 5ms audit overhead)
- Multi-tenant security validation

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

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

docs/plans/sprint_2_story_3.md

@@ -0,0 +1,105 @@
+---
+story_id: sprint_2_story_3
+sprint: sprint_2
+priority: P1
+status: not_started
+story_points: 8
+estimated_days: 3-4
+created_date: 2025-11-05
+assignee: Backend Team
+---
+
+# Story 3: Sprint Management Module
+
+**Sprint**: Sprint 2
+**Priority**: P1 (Should Have)
+**Estimated**: 3-4 days (Day 31-34)
+**Owner**: Backend Team
+
+## Description
+
+Implement complete Sprint management functionality to support agile sprint planning, tracking, and burndown analytics. Enable teams to organize work into time-boxed iterations.
+
+## Acceptance Criteria
+
+- [ ] Sprint entity created with proper domain logic
+- [ ] 9 CQRS API endpoints implemented (Create, Update, Delete, Get, List, Start, Complete, AddTask, RemoveTask)
+- [ ] Burndown chart data calculation implemented
+- [ ] SignalR real-time notifications for Sprint events
+- [ ] Multi-tenant isolation enforced
+- [ ] Integration tests with >= 90% coverage
+- [ ] All tests passing
+
+## Technical Requirements
+
+**Sprint Entity**:
+- Fields: `SprintId`, `TenantId`, `ProjectId`, `Name`, `Goal`, `StartDate`, `EndDate`, `Status` (Planned/Active/Completed)
+- Relationships: `Project` (many-to-one), `Tasks` (one-to-many)
+- Business Logic: Validate dates, status transitions, capacity tracking
+
+**API Endpoints**:
+1. POST /api/sprints - Create Sprint
+2. PUT /api/sprints/{id} - Update Sprint
+3. DELETE /api/sprints/{id} - Delete Sprint
+4. GET /api/sprints/{id} - Get Sprint by ID
+5. GET /api/sprints - List Sprints (with filters)
+6. POST /api/sprints/{id}/start - Start Sprint
+7. POST /api/sprints/{id}/complete - Complete Sprint
+8. POST /api/sprints/{id}/tasks/{taskId} - Add Task to Sprint
+9. DELETE /api/sprints/{id}/tasks/{taskId} - Remove Task from Sprint
+
+**Burndown Chart**:
+- Calculate remaining story points per day
+- Track completed vs remaining work
+- Return data for chart visualization
+
+**Technology Stack**:
+- Domain Layer: Sprint aggregate root + domain events
+- Application Layer: CQRS (5 commands + 4 queries)
+- Infrastructure Layer: PostgreSQL + EF Core
+- Real-time: SignalR SprintHub
+
+## Tasks
+
+- [ ] [Task 1](sprint_2_story_3_task_1.md) - Create Sprint Aggregate Root and Domain Events
+- [ ] [Task 2](sprint_2_story_3_task_2.md) - Implement Sprint Repository and EF Core Configuration
+- [ ] [Task 3](sprint_2_story_3_task_3.md) - Create CQRS Commands and Queries
+- [ ] [Task 4](sprint_2_story_3_task_4.md) - Implement Burndown Chart Calculation
+- [ ] [Task 5](sprint_2_story_3_task_5.md) - Add SignalR Real-Time Notifications
+- [ ] [Task 6](sprint_2_story_3_task_6.md) - Write Integration Tests
+
+**Progress**: 0/6 tasks completed
+
+## Dependencies
+
+**Prerequisites**:
+- ✅ ProjectManagement Module 95% Production Ready (Day 16)
+- ✅ SignalR Backend 100% Complete (Day 17)
+- ✅ Multi-Tenant Security Complete (Day 15)
+
+## Definition of Done
+
+- All 6 tasks completed
+- 9 API endpoints working
+- Burndown chart data calculation implemented
+- SignalR notifications working
+- All tests passing (>= 90% coverage)
+- Multi-tenant isolation verified
+- Code reviewed and approved
+- Git commit created
+
+## Notes
+
+**Sprint Lifecycle**:
+1. Planned → Active (Start Sprint)
+2. Active → Completed (Complete Sprint)
+3. Cannot delete Active sprint (must complete first)
+
+**Burndown Chart Formula**:
+- Total Story Points = Sum of all tasks in sprint
+- Remaining Story Points = Sum of incomplete tasks
+- Daily Burndown = [(Start Date, Total), ..., (Today, Remaining), ..., (End Date, 0 ideal)]
+
+---
+
+**Created**: 2025-11-05 by Backend Agent