feat: add tenant and user management with migrations, handlers, and tests

- Implemented tenant and user management features including:
  - Tenant creation and management with associated migrations.
  - User creation and management with associated migrations.
  - Tenant membership management with associated migrations.
  - Platform user roles management with associated migrations.
  - Quota management with associated migrations.
  - Article and template management with associated migrations.
- Added HTTP handlers for templates and workspaces.
- Created tests for protected and public routes.
- Introduced a script to check tenant scope in SQL queries.
- Documented task plan for backend completion and frontend foundation.

server/internal/tenant/repository/tx.go

@@ -0,0 +1,43 @@
+package repository
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgconn"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+type DBTX interface {
+	Exec(ctx context.Context, sql string, args ...any) (pgconn.CommandTag, error)
+	Query(ctx context.Context, sql string, args ...any) (pgx.Rows, error)
+	QueryRow(ctx context.Context, sql string, args ...interface{}) pgx.Row
+}
+
+type TxManager struct {
+	pool *pgxpool.Pool
+}
+
+func NewTxManager(pool *pgxpool.Pool) *TxManager {
+	return &TxManager{pool: pool}
+}
+
+func (m *TxManager) WithTx(ctx context.Context, fn func(tx pgx.Tx) error) error {
+	tx, err := m.pool.Begin(ctx)
+	if err != nil {
+		return fmt.Errorf("begin tx: %w", err)
+	}
+	defer func() {
+		_ = tx.Rollback(ctx)
+	}()
+
+	if err := fn(tx); err != nil {
+		return err
+	}
+	return tx.Commit(ctx)
+}
+
+func (m *TxManager) Pool() *pgxpool.Pool {
+	return m.pool
+}