feat(backend): Implement complete Issue Management Module

Implemented full-featured Issue Management module following Clean Architecture,
DDD, CQRS and Event Sourcing patterns to support Kanban board functionality.

## Domain Layer
- Issue aggregate root with business logic
- IssueType, IssueStatus, IssuePriority enums
- Domain events: IssueCreated, IssueUpdated, IssueStatusChanged, IssueAssigned, IssueDeleted
- IIssueRepository and IUnitOfWork interfaces
- Domain exceptions (DomainException, NotFoundException)

## Application Layer
- **Commands**: CreateIssue, UpdateIssue, ChangeIssueStatus, AssignIssue, DeleteIssue
- **Queries**: GetIssueById, ListIssues, ListIssuesByStatus
- Command/Query handlers with validation
- FluentValidation validators for all commands
- Event handlers for domain events
- IssueDto for data transfer
- ValidationBehavior pipeline

## Infrastructure Layer
- IssueManagementDbContext with EF Core 9.0
- IssueConfiguration for entity mapping
- IssueRepository implementation
- UnitOfWork implementation
- Multi-tenant support with TenantId filtering
- Optimized indexes for query performance

## API Layer
- IssuesController with full REST API
  - GET /api/v1/projects/{projectId}/issues (list with optional status filter)
  - GET /api/v1/projects/{projectId}/issues/{id} (get by id)
  - POST /api/v1/projects/{projectId}/issues (create)
  - PUT /api/v1/projects/{projectId}/issues/{id} (update)
  - PUT /api/v1/projects/{projectId}/issues/{id}/status (change status for Kanban)
  - PUT /api/v1/projects/{projectId}/issues/{id}/assign (assign to user)
  - DELETE /api/v1/projects/{projectId}/issues/{id} (delete)
- Request models: CreateIssueRequest, UpdateIssueRequest, ChangeStatusRequest, AssignIssueRequest
- JWT authentication required
- Real-time SignalR notifications integrated

## Module Registration
- Added AddIssueManagementModule extension method
- Registered in Program.cs
- Added IMDatabase connection string
- Added project references to ColaFlow.API.csproj

## Architecture Patterns
- ✅ Clean Architecture (Domain, Application, Infrastructure, API layers)
- ✅ DDD (Aggregate roots, value objects, domain events)
- ✅ CQRS (Command/Query separation)
- ✅ Event Sourcing (Domain events with MediatR)
- ✅ Repository Pattern (IIssueRepository)
- ✅ Unit of Work (Transactional consistency)
- ✅ Dependency Injection
- ✅ FluentValidation
- ✅ Multi-tenancy support

## Real-time Features
- SignalR integration via IRealtimeNotificationService
- NotifyIssueCreated, NotifyIssueUpdated, NotifyIssueStatusChanged, NotifyIssueAssigned, NotifyIssueDeleted
- Project-level broadcasting for collaborative editing

## Next Steps
1. Stop running API process if exists
2. Run: dotnet ef migrations add InitialIssueModule --context IssueManagementDbContext --startup-project ../../../ColaFlow.API
3. Run: dotnet ef database update --context IssueManagementDbContext --startup-project ../../../ColaFlow.API
4. Create test scripts
5. Verify all CRUD operations and real-time notifications

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

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

colaflow-api/src/ColaFlow.API/Extensions/ModuleExtensions.cs

@@ -6,6 +6,9 @@ using ColaFlow.Modules.ProjectManagement.Application.Commands.CreateProject;
 using ColaFlow.Modules.ProjectManagement.Domain.Repositories;
 using ColaFlow.Modules.ProjectManagement.Infrastructure.Persistence;
 using ColaFlow.Modules.ProjectManagement.Infrastructure.Repositories;
+using ColaFlow.Modules.IssueManagement.Application.Commands.CreateIssue;
+using ColaFlow.Modules.IssueManagement.Infrastructure.Persistence;
+using ColaFlow.Modules.IssueManagement.Infrastructure.Persistence.Repositories;
 using Microsoft.Extensions.Hosting;
 
 namespace ColaFlow.API.Extensions;
@@ -35,7 +38,7 @@ public static class ModuleExtensions
 
         // Register repositories
         services.AddScoped<IProjectRepository, ProjectRepository>();
-        services.AddScoped<IUnitOfWork, UnitOfWork>();
+        services.AddScoped<IUnitOfWork, ColaFlow.Modules.ProjectManagement.Infrastructure.Persistence.UnitOfWork>();
 
         // Register MediatR handlers from Application assembly (v13.x syntax)
         services.AddMediatR(cfg =>
@@ -54,4 +57,43 @@ public static class ModuleExtensions
 
         return services;
     }
+
+    /// <summary>
+    /// Register IssueManagement Module
+    /// </summary>
+    public static IServiceCollection AddIssueManagementModule(
+        this IServiceCollection services,
+        IConfiguration configuration,
+        IHostEnvironment? environment = null)
+    {
+        // Only register PostgreSQL DbContext in non-Testing environments
+        if (environment == null || environment.EnvironmentName != "Testing")
+        {
+            // Register DbContext
+            var connectionString = configuration.GetConnectionString("IMDatabase");
+            services.AddDbContext<IssueManagementDbContext>(options =>
+                options.UseNpgsql(connectionString));
+        }
+
+        // Register repositories
+        services.AddScoped<ColaFlow.Modules.IssueManagement.Domain.Repositories.IIssueRepository, IssueRepository>();
+        services.AddScoped<ColaFlow.Modules.IssueManagement.Domain.Repositories.IUnitOfWork, ColaFlow.Modules.IssueManagement.Infrastructure.Persistence.Repositories.UnitOfWork>();
+
+        // Register MediatR handlers from Application assembly
+        services.AddMediatR(cfg =>
+        {
+            cfg.LicenseKey = configuration["MediatR:LicenseKey"];
+            cfg.RegisterServicesFromAssembly(typeof(CreateIssueCommand).Assembly);
+        });
+
+        // Register FluentValidation validators
+        services.AddValidatorsFromAssembly(typeof(CreateIssueCommand).Assembly);
+
+        // Register pipeline behaviors
+        services.AddTransient(typeof(IPipelineBehavior<,>), typeof(ColaFlow.Modules.IssueManagement.Application.Behaviors.ValidationBehavior<,>));
+
+        Console.WriteLine("[IssueManagement] Module registered");
+
+        return services;
+    }
 }