fix(issue-16): fix critical transaction bug and high-severity repository issues

C1: CreateBatch shadowed err with := in loop, causing partial commits on
    failure. Fixed with named return and execErr loop variable.
H1: OrderBy concatenated raw into SQL query. Added whitelist validation.
H2: Organization.List dropped query args in SelectContext call.
H3: CourseRepository.Get wrapped sql.ErrNoRows without translating to
    ErrNotFound, breaking the port contract.
Medium: Create now returns the created entity via Get; fixed prepared
    statement leak in Organization.Create; unified time.Now() to UTC.

internal/kurious/adapters/sqlite_course_repository.go

@@ -9,6 +9,7 @@ import (
 	"strings"
 	"time"
 
+	cerrors "git.loyso.art/frx/kurious/internal/common/errors"
 	"git.loyso.art/frx/kurious/internal/common/nullable"
 	"git.loyso.art/frx/kurious/internal/common/xslices"
 	"git.loyso.art/frx/kurious/internal/kurious/domain"
@@ -72,6 +73,14 @@ func (r *sqliteCourseRepository) List(
 		params.OrderBy = "id"
 	}
 
+	var allowedOrderFields = map[string]bool{
+		"id": true, "full_price": true, "name": true,
+		"discount": true, "duration": true, "starts_at": true,
+	}
+	if !allowedOrderFields[params.OrderBy] {
+		params.OrderBy = "id"
+	}
+
 	direction := "ASC"
 	if !params.Ascending {
 		direction = "DESC"
@@ -277,6 +286,9 @@ func (r *sqliteCourseRepository) Get(
 	var courseDB sqliteCourseDB
 	err = r.db.GetContext(ctx, &courseDB, query, id)
 	if err != nil {
+		if errors.Is(err, sql.ErrNoRows) {
+			return course, cerrors.ErrNotFound
+		}
 		return course, fmt.Errorf("executing query: %w", err)
 	}
 
@@ -289,7 +301,7 @@ func (r *sqliteCourseRepository) GetByExternalID(
 	return course, errors.New("not implemented")
 }
 
-func (r *sqliteCourseRepository) CreateBatch(ctx context.Context, params ...domain.CreateCourseParams) error {
+func (r *sqliteCourseRepository) CreateBatch(ctx context.Context, params ...domain.CreateCourseParams) (err error) {
 	tx, err := r.db.BeginTxx(ctx, &sql.TxOptions{Isolation: sql.LevelDefault})
 	if err != nil {
 		return fmt.Errorf("beginning tx: %w", err)
@@ -317,9 +329,9 @@ func (r *sqliteCourseRepository) CreateBatch(ctx context.Context, params ...doma
 	}
 
 	for _, param := range params {
-		_, err := stmt.ExecContext(ctx, createCourseParamsAsValues(param)...)
+		_, execErr := stmt.ExecContext(ctx, createCourseParamsAsValues(param)...)
-		if err != nil {
+		if execErr != nil {
-			return fmt.Errorf("executing statement query: %w", err)
+			return fmt.Errorf("executing statement query: %w", execErr)
 		}
 	}
 
@@ -328,7 +340,10 @@ func (r *sqliteCourseRepository) CreateBatch(ctx context.Context, params ...doma
 
 func (r *sqliteCourseRepository) Create(ctx context.Context, params domain.CreateCourseParams) (domain.Course, error) {
 	err := r.CreateBatch(ctx, params)
+	if err != nil {
 		return domain.Course{}, err
+	}
+	return r.Get(ctx, params.ID)
 }
 
 func (r *sqliteCourseRepository) UpdateCourseDescription(ctx context.Context, id, description string) error {
@@ -411,7 +426,7 @@ func scanRows(ctx context.Context, db *sqlx.DB, f func(rowsScanner) error, query
 }
 
 func createCourseParamsAsValues(params domain.CreateCourseParams) []any {
-	now := time.Now()
+	now := time.Now().UTC()
 
 	return []any{
 		params.ID,

internal/kurious/adapters/sqlite_organization_repository.go

@@ -187,7 +187,7 @@ func (r *sqliteOrganizationRepository) List(ctx context.Context, params domain.L
 	}()
 
 	organizations := make([]organizationDB, 0, 1<<8)
-	err = r.db.SelectContext(ctx, &organizations, query)
+	err = r.db.SelectContext(ctx, &organizations, query, args...)
 	if err != nil {
 		return nil, fmt.Errorf("executing query: %w", err)
 	}
@@ -262,6 +262,7 @@ func (r *sqliteOrganizationRepository) Create(ctx context.Context, params domain
 	if err != nil {
 		return out, fmt.Errorf("preparing statement: %w", err)
 	}
+	defer stmt.Close()
 
 	var orgdb organizationDB