Function execute_migration_plan 

pub async fn execute_migration_plan(
    migration_pool: &Pool,
    config_pool: &Pool,
    plan: &MigrationPlan,
    migration_plan_id: &str,
    package_id: &str,
    tenant_id: &str,
    from_version: Option<&str>,
    to_version: &str,
    dialect: &dyn Dialect,
) -> Result<MigrationExecutionResult, AppError>

Execute a pre-computed MigrationPlan against the tenant database.

The plan is reconciled against the database’s actual state first (see reconcile_step), so steps whose effect is already present are skipped instead of failing the whole migration. Writes per-step audit records to the config (architect) database. Returns counts and any warning messages collected from best-effort failures.