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/auditlog_query.go

@@ -262,12 +262,12 @@ func (_q *AuditLogQuery) Clone() *AuditLogQuery {
 // Example:
 //
 //	var v []struct {
-//		ActorID string `json:"actor_id,omitempty"`
+//		UserID string `json:"user_id,omitempty"`
 //		Count int `json:"count,omitempty"`
 //	}
 //
 //	client.AuditLog.Query().
-//		GroupBy(auditlog.FieldActorID).
+//		GroupBy(auditlog.FieldUserID).
 //		Aggregate(ent.Count()).
 //		Scan(ctx, &v)
 func (_q *AuditLogQuery) GroupBy(field string, fields ...string) *AuditLogGroupBy {
@@ -285,11 +285,11 @@ func (_q *AuditLogQuery) GroupBy(field string, fields ...string) *AuditLogGroupB
 // Example:
 //
 //	var v []struct {
-//		ActorID string `json:"actor_id,omitempty"`
+//		UserID string `json:"user_id,omitempty"`
 //	}
 //
 //	client.AuditLog.Query().
-//		Select(auditlog.FieldActorID).
+//		Select(auditlog.FieldUserID).
 //		Scan(ctx, &v)
 func (_q *AuditLogQuery) Select(fields ...string) *AuditLogSelect {
 	_q.ctx.Fields = append(_q.ctx.Fields, fields...)