fix(backend): Fix Integration Test database provider conflict with environment-aware DI

Implement environment-aware dependency injection to resolve EF Core provider conflict
in Integration Tests. The issue was caused by both PostgreSQL and InMemory providers
being registered in the same service provider.

Changes:
- Modified Identity Module DependencyInjection to skip PostgreSQL DbContext registration in Testing environment
- Modified ProjectManagement Module ModuleExtensions with same environment check
- Updated Program.cs to pass IHostEnvironment to both module registration methods
- Added Microsoft.Extensions.Hosting.Abstractions package to Identity.Infrastructure project
- Updated ColaFlowWebApplicationFactory to set Testing environment and register InMemory databases
- Simplified WebApplicationFactory by removing complex RemoveAll logic

Results:
- All 31 Integration Tests now run (previously only 1 ran)
- No EF Core provider conflict errors
- 23 tests pass, 8 tests fail (failures are business logic issues, not infrastructure)
- Production environment still uses PostgreSQL as expected

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

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

colaflow-api/src/ColaFlow.API/Program.cs

@@ -10,11 +10,11 @@ using System.Text;
 var builder = WebApplication.CreateBuilder(args);
 
 // Register ProjectManagement Module
-builder.Services.AddProjectManagementModule(builder.Configuration);
+builder.Services.AddProjectManagementModule(builder.Configuration, builder.Environment);
 
 // Register Identity Module
 builder.Services.AddIdentityApplication();
-builder.Services.AddIdentityInfrastructure(builder.Configuration);
+builder.Services.AddIdentityInfrastructure(builder.Configuration, builder.Environment);
 
 // Add controllers
 builder.Services.AddControllers();
@@ -107,3 +107,6 @@ app.UseAuthorization();
 app.MapControllers();
 
 app.Run();
+
+// Make the implicit Program class public for integration tests
+public partial class Program { }