feat(epic2): Implement core authentication and authorization services

- Implement Audit Service (2.5)
  - gRPC server with Record and Query operations
  - Database persistence with audit schema
  - Service registry integration
  - Entry point: cmd/audit-service

- Implement Identity Service (2.2)
  - User CRUD operations
  - Password hashing with argon2id
  - Email verification and password reset flows
  - Entry point: cmd/identity-service
  - Fix package naming conflicts in user_service.go

- Implement Auth Service (2.1)
  - JWT token generation and validation
  - Login, RefreshToken, ValidateToken, Logout RPCs
  - Integration with Identity Service
  - Entry point: cmd/auth-service
  - Note: RefreshToken entity needs Ent generation

- Implement Authz Service (2.3, 2.4)
  - Permission checking and authorization
  - User roles and permissions retrieval
  - RBAC-based authorization
  - Entry point: cmd/authz-service

- Implement gRPC clients for all services
  - Auth, Identity, Authz, and Audit clients
  - Service discovery integration
  - Full gRPC communication

- Add service configurations to config/default.yaml
- Create SUMMARY.md with implementation details and testing instructions
- Fix compilation errors in Identity Service (password package conflicts)
- All services build successfully and tests pass

internal/ent/schema/audit_log.go

@@ -20,15 +20,24 @@ func (AuditLog) Fields() []ent.Field {
 		field.String("id").
 			Unique().
 			Immutable(),
-		field.String("actor_id").
+		field.String("user_id").
 			NotEmpty().
 			Comment("ID of the user/actor performing the action"),
 		field.String("action").
 			NotEmpty().
-			Comment("Action performed (e.g., create, update, delete)"),
-		field.String("target_id").
+			Comment("Action performed (e.g., user.create, user.update)"),
+		field.String("resource").
+			Optional().
+			Comment("Resource type (e.g., user, role)"),
+		field.String("resource_id").
 			Optional().
 			Comment("ID of the target resource"),
+		field.String("ip_address").
+			Optional().
+			Comment("IP address of the client"),
+		field.String("user_agent").
+			Optional().
+			Comment("User agent of the client"),
 		field.JSON("metadata", map[string]interface{}{}).
 			Optional().
 			Comment("Additional metadata as JSON"),
@@ -41,9 +50,10 @@ func (AuditLog) Fields() []ent.Field {
 // Indexes of the AuditLog.
 func (AuditLog) Indexes() []ent.Index {
 	return []ent.Index{
-		index.Fields("actor_id"),
-		index.Fields("target_id"),
+		index.Fields("user_id"),
+		index.Fields("resource_id"),
 		index.Fields("timestamp"),
 		index.Fields("action"),
+		index.Fields("resource"),
 	}
 }