feat(backend): Implement email verification flow - Phase 2

Add complete email verification system with token-based verification.

Changes:
- Created EmailVerificationToken domain entity with expiration and verification tracking
- Created EmailVerifiedEvent domain event for audit trail
- Updated User entity with IsEmailVerified property and VerifyEmail method
- Created IEmailVerificationTokenRepository interface and implementation
- Created SecurityTokenService for secure token generation and SHA-256 hashing
- Created EmailVerificationTokenConfiguration for EF Core mapping
- Updated IdentityDbContext to include EmailVerificationTokens DbSet
- Created SendVerificationEmailCommand and handler for sending verification emails
- Created VerifyEmailCommand and handler for email verification
- Added POST /api/auth/verify-email endpoint to AuthController
- Integrated email verification into RegisterTenantCommandHandler
- Registered all new services in DependencyInjection
- Created and applied AddEmailVerification database migration
- Build successful with no compilation errors

Database Schema:
- email_verification_tokens table with indexes on token_hash and user_id
- 24-hour token expiration
- One-time use tokens with verification tracking

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

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

colaflow-api/src/Modules/Identity/ColaFlow.Modules.Identity.Infrastructure/DependencyInjection.cs

@@ -37,11 +37,13 @@ public static class DependencyInjection
         services.AddScoped<IUserRepository, UserRepository>();
         services.AddScoped<IRefreshTokenRepository, RefreshTokenRepository>();
         services.AddScoped<IUserTenantRoleRepository, UserTenantRoleRepository>();
+        services.AddScoped<IEmailVerificationTokenRepository, EmailVerificationTokenRepository>();
 
         // Application Services
         services.AddScoped<IJwtService, JwtService>();
         services.AddScoped<IPasswordHasher, PasswordHasher>();
         services.AddScoped<IRefreshTokenService, RefreshTokenService>();
+        services.AddScoped<ISecurityTokenService, SecurityTokenService>();
 
         // Email Services
         var emailProvider = configuration["Email:Provider"] ?? "Mock";