feat: init migrations for transactional tables (#9946)

# Which Problems Are Solved

To start with transactional tables we need to setup the new `zitadel`
schema in a way that does not rely on the event store later.

# How the Problems Are Solved

Setup step added which calls the function which executes the migrations.

# Additional Changes

none

# Additional Context

- closes #9933

backend/v3/storage/database/dialect/postgres/conn.go

@@ -6,11 +6,15 @@ import (
 	"github.com/jackc/pgx/v5/pgxpool"
 
 	"github.com/zitadel/zitadel/backend/v3/storage/database"
+	"github.com/zitadel/zitadel/backend/v3/storage/database/dialect/postgres/migration"
 )
 
 type pgxConn struct{ *pgxpool.Conn }
 
-var _ database.Client = (*pgxConn)(nil)
+var (
+	_ database.Client   = (*pgxConn)(nil)
+	_ database.Migrator = (*pgxConn)(nil)
+)
 
 // Release implements [database.Client].
 func (c *pgxConn) Release(_ context.Context) error {
@@ -46,3 +50,8 @@ func (c *pgxConn) Exec(ctx context.Context, sql string, args ...any) error {
 	_, err := c.Conn.Exec(ctx, sql, args...)
 	return err
 }
+
+// Migrate implements [database.Migrator].
+func (c *pgxConn) Migrate(ctx context.Context) error {
+	return migration.Migrate(ctx, c.Conn.Conn())
+}