Refactor Alembic command execution in Jenkinsfile and remove obsolete script

- Updated the Alembic upgrade command in the Jenkinsfile to directly use Python for execution, eliminating reliance on a separate shell script that caused issues with command parsing.
- Revised comments to clarify the changes and their implications for the command context during E2E testing.
- Deleted the now-unnecessary jenkins-alembic-e2e.sh script to streamline the process.

Jenkinsfile

@@ -284,8 +284,8 @@ pipeline {
             e2e_compose_fail_logs
             exit 1
           fi
-          # Script en el repo: Groovy/CI mutila comillas de -c o asignación VAR='…;…' (mismo síntoma: test en host)
-          if ! e2e_compose run --rm --no-deps --entrypoint /bin/sh backend /app/scripts/jenkins-alembic-e2e.sh; then
+          # Sin sh -c ni .sh bajo /app: sin comillas frágiles y sin depender de un fichero no montado aún (push)
+          if ! e2e_compose run --rm --no-deps --entrypoint python3 backend -m alembic -c /app/alembic.ini upgrade head; then
             echo "ERROR: falló alembic upgrade head (job previo al stack completo)"
             e2e_compose_fail_logs
             exit 1

backend/scripts/jenkins-alembic-e2e.sh

@@ -1,7 +0,0 @@
-#!/bin/sh
-# Ejecutado solo desde Jenkins E2E: docker compose run --entrypoint /bin/sh … backend /app/scripts/jenkins-alembic-e2e.sh
-# (evita pasar cadenas con ';' a -c: Groovy/CI rompe comillas y parte el comando)
-set -eux
-test -f /app/alembic.ini
-cd /app
-exec alembic -c /app/alembic.ini upgrade head