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/tests/Modules/Identity/ColaFlow.Modules.Identity.IntegrationTests/Infrastructure/ColaFlowWebApplicationFactory.cs

@@ -0,0 +1,132 @@
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Mvc.Testing;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.DependencyInjection.Extensions;
+using Microsoft.Extensions.Hosting;
+using ColaFlow.Modules.Identity.Infrastructure.Persistence;
+using ColaFlow.Modules.ProjectManagement.Infrastructure.Persistence;
+
+namespace ColaFlow.Modules.Identity.IntegrationTests.Infrastructure;
+
+/// <summary>
+/// Custom WebApplicationFactory for ColaFlow Integration Tests
+/// Supports both In-Memory and Real PostgreSQL databases
+/// </summary>
+public class ColaFlowWebApplicationFactory : WebApplicationFactory<Program>
+{
+    private readonly bool _useInMemoryDatabase;
+    private readonly string? _testDatabaseName;
+
+    public ColaFlowWebApplicationFactory(bool useInMemoryDatabase = true, string? testDatabaseName = null)
+    {
+        _useInMemoryDatabase = useInMemoryDatabase;
+        _testDatabaseName = testDatabaseName ?? $"TestDb_{Guid.NewGuid()}";
+    }
+
+    protected override void ConfigureWebHost(IWebHostBuilder builder)
+    {
+        // Set environment to Testing - this prevents PostgreSQL DbContext registration in modules
+        builder.UseEnvironment("Testing");
+
+        // Configure test-specific settings
+        builder.ConfigureAppConfiguration((context, config) =>
+        {
+            // Clear existing connection strings to prevent PostgreSQL registration
+            config.Sources.Clear();
+
+            // Add minimal config for testing
+            config.AddInMemoryCollection(new Dictionary<string, string?>
+            {
+                ["ConnectionStrings:DefaultConnection"] = "",
+                ["ConnectionStrings:PMDatabase"] = "",
+                ["Jwt:SecretKey"] = "test-secret-key-for-integration-tests-minimum-32-characters",
+                ["Jwt:Issuer"] = "ColaFlow.Test",
+                ["Jwt:Audience"] = "ColaFlow.Test",
+                ["Jwt:AccessTokenExpirationMinutes"] = "15",
+                ["Jwt:RefreshTokenExpirationDays"] = "7"
+            });
+        });
+
+        builder.ConfigureServices(services =>
+        {
+            // Register test databases (modules won't register PostgreSQL due to Testing environment)
+            if (_useInMemoryDatabase)
+            {
+                // Use In-Memory Database for fast, isolated tests
+                // IMPORTANT: Share the same database name for cross-context data consistency
+                services.AddDbContext<IdentityDbContext>(options =>
+                {
+                    options.UseInMemoryDatabase(_testDatabaseName!);
+                    options.EnableSensitiveDataLogging();
+                });
+
+                services.AddDbContext<PMDbContext>(options =>
+                {
+                    options.UseInMemoryDatabase(_testDatabaseName!);
+                    options.EnableSensitiveDataLogging();
+                });
+            }
+            else
+            {
+                // Use Real PostgreSQL for integration tests
+                var connectionString = $"Host=localhost;Port=5432;Database=colaflow_test_{_testDatabaseName};Username=postgres;Password=postgres";
+
+                services.AddDbContext<IdentityDbContext>(options =>
+                {
+                    options.UseNpgsql(connectionString);
+                    options.EnableSensitiveDataLogging();
+                });
+
+                services.AddDbContext<PMDbContext>(options =>
+                {
+                    options.UseNpgsql(connectionString);
+                    options.EnableSensitiveDataLogging();
+                });
+            }
+        });
+    }
+
+    // Override CreateHost to initialize databases after the host is created
+    protected override IHost CreateHost(IHostBuilder builder)
+    {
+        var host = base.CreateHost(builder);
+
+        // Initialize databases after host is created
+        using var scope = host.Services.CreateScope();
+        var services = scope.ServiceProvider;
+
+        try
+        {
+            // Initialize Identity database
+            var identityDb = services.GetRequiredService<IdentityDbContext>();
+            if (_useInMemoryDatabase)
+            {
+                identityDb.Database.EnsureCreated();
+            }
+            else
+            {
+                identityDb.Database.Migrate();
+            }
+
+            // Initialize ProjectManagement database
+            var pmDb = services.GetRequiredService<PMDbContext>();
+            if (_useInMemoryDatabase)
+            {
+                pmDb.Database.EnsureCreated();
+            }
+            else
+            {
+                pmDb.Database.Migrate();
+            }
+        }
+        catch (Exception ex)
+        {
+            Console.WriteLine($"Error initializing test database: {ex.Message}");
+            throw;
+        }
+
+        return host;
+    }
+}