fix(groups): conservar el historial de un grupo al borrarlo

backend/controllers/group/group-controller.ts

@@ -253,7 +253,7 @@ export class GroupController {
         })
       }
 
-      const deleted = await GroupRepository.delete(groupId)
+      const deleted = await GroupRepository.delete(groupId, userId, group)
 
       if (!deleted) {
         return res.status(500).json({

backend/db-mysql/INDEX.md

@@ -108,6 +108,7 @@ db-mysql/
 | 2026-10-05 | `20261005_complete_fresh_install.sql`                   | Completa una instalación desde cero: el baseline congelado no crea `cashier_history` (nombre de clave duplicado), `scheduling_assignments` (referencia a una tabla creada después) ni `demo_activity_log`, y deja `roles.name` en `varchar(50)`. Definiciones copiadas de Aiven. En Aiven no cambia nada; en local creó `demo_activity_log`, que faltaba. `pnpm setup:local` además corrige esos dos fallos del baseline en memoria. | ✅ local · ✅ Aiven (sin cambios) |
 | 2026-10-05 | `20261005_fix_bo_monthly_summary_view.sql`              | Recrea `v_bo_monthly_summary` con `period` en el `GROUP BY`. Con `ONLY_FULL_GROUP_BY` (activo en Aiven y local) toda consulta a la vista fallaba con el error 1055 y `GET /api/backoffice/stats/monthly` respondía siempre 500. Mismas columnas y mismos grupos; comprobada contra un cálculo directo sobre `bo_invoices`. | ✅ local · ✅ Aiven |
 | 2026-10-05 | `20261005_drop_demo_admin_role.sql`                     | Borra el rol `demo-admin` si ningún usuario lo tiene (ADR-038): la cuenta demo es un admin con `is_demo` y el código ya no conoce ese rol. En local no existía. | ✅ local (sin cambios) · ✅ Aiven |
+| 2026-10-11 | `20261011_keep_group_history_on_delete.sql` | Quita la clave foránea `group_history_ibfk_1` (`ON DELETE CASCADE` a `hotel_groups`): borrar un grupo ya no borra su historial, y el borrado deja una fila `deleted` con la foto del grupo. **Aplicar en Aiven antes de desplegar el código**: con la clave dentro, borrar un grupo falla. | ✅ local · ✅ Aiven |
 
 ### Verificación (99)
 

backend/db-mysql/scripts/20261011_keep_group_history_on_delete.sql

@@ -0,0 +1,40 @@
+-- =============================================================================
+-- 20261011_keep_group_history_on_delete.sql
+-- =============================================================================
+-- Drops the foreign key from group_history.group_id to hotel_groups.id. It was
+-- ON DELETE CASCADE, so deleting a group also deleted its whole history and
+-- left no trace of the deletion. Decided on 2026-10-11: a group is still
+-- deleted, but its history stays and gains a "deleted" row with a snapshot of
+-- the group (GroupRepository.delete). group_id keeps its index
+-- (idx_group_id); rows of a deleted group point to an id that no longer
+-- exists.
+--
+-- Idempotent: if the foreign key is already gone the ALTER is a no-op.
+-- Safe to run multiple times.
+--
+-- Applies to: LOCAL + AIVEN. Apply it before deploying the code that writes
+-- the deletion row: with the foreign key in place that insert fails and the
+-- delete rolls back.
+-- Rollback (only while no history row points to a deleted group):
+--   ALTER TABLE group_history ADD CONSTRAINT group_history_ibfk_1
+--     FOREIGN KEY (group_id) REFERENCES hotel_groups (id) ON DELETE CASCADE;
+-- =============================================================================
+
+SET @fk_exists := (
+  SELECT COUNT(*)
+  FROM information_schema.TABLE_CONSTRAINTS
+  WHERE TABLE_SCHEMA = DATABASE()
+    AND TABLE_NAME = 'group_history'
+    AND CONSTRAINT_NAME = 'group_history_ibfk_1'
+    AND CONSTRAINT_TYPE = 'FOREIGN KEY'
+);
+
+SET @ddl := IF(
+  @fk_exists = 1,
+  'ALTER TABLE group_history DROP FOREIGN KEY group_history_ibfk_1',
+  'SELECT ''group_history_ibfk_1 already dropped, skipping'' AS info'
+);
+
+PREPARE stmt FROM @ddl;
+EXECUTE stmt;
+DEALLOCATE PREPARE stmt;

backend/repositories/group/group-repository.ts

@@ -269,9 +269,33 @@ export class GroupRepository {
   /**
    * Eliminar grupo
    */
-  static async delete(id: number): Promise<boolean> {
-    const [result] = await db.query<ResultSetHeader>('DELETE FROM hotel_groups WHERE id = ?', [id])
-    return result.affectedRows > 0
+  static async delete(id: number, deletedBy: string, snapshot: unknown): Promise<boolean> {
+    // The group goes, its history stays: group_history has no foreign key to
+    // hotel_groups since 20261011_keep_group_history_on_delete.sql. The delete
+    // and its history row commit or roll back together
+    const connection = await db.getConnection()
+    try {
+      await connection.beginTransaction()
+      const [result] = await connection.query<ResultSetHeader>(
+        'DELETE FROM hotel_groups WHERE id = ?',
+        [id]
+      )
+      if (result.affectedRows > 0) {
+        await connection.query(
+          `INSERT INTO group_history
+           (group_id, action, table_affected, record_id, old_value, changed_by, notes)
+           VALUES (?, 'deleted', 'hotel_groups', ?, ?, ?, 'Grupo eliminado')`,
+          [id, id, JSON.stringify(snapshot), deletedBy]
+        )
+      }
+      await connection.commit()
+      return result.affectedRows > 0
+    } catch (error) {
+      await connection.rollback()
+      throw error
+    } finally {
+      connection.release()
+    }
   }
 
   /**

backend/tests/group/group-deletion.test.ts

@@ -0,0 +1,78 @@
+// tests/group/group-deletion.test.ts
+// Regression tests: deleting a group deleted its whole history too
+// (group_history had ON DELETE CASCADE) and logged nothing. Decided on
+// 2026-10-11: the group is still deleted, its history stays, and the delete
+// writes a "deleted" row with a snapshot of the group, in the same
+// transaction.
+
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+import { readFileSync } from 'node:fs'
+import { join, dirname } from 'node:path'
+import { fileURLToPath } from 'node:url'
+
+const connection = {
+  beginTransaction: vi.fn(),
+  commit: vi.fn(),
+  rollback: vi.fn(),
+  release: vi.fn(),
+  query: vi.fn(),
+}
+
+vi.mock('../../config/db.js', () => ({
+  default: { getConnection: vi.fn(async () => connection), query: vi.fn() },
+}))
+
+const { GroupRepository } = await import('../../repositories/group/group-repository.js')
+
+const group = { id: 4, name: 'Congreso', total_amount: '12500.00' }
+
+describe('deleting a group', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+    connection.query.mockReset()
+  })
+
+  it('deletes the group and writes a deleted row with its snapshot', async () => {
+    connection.query.mockResolvedValueOnce([{ affectedRows: 1 }]).mockResolvedValueOnce([{}])
+
+    expect(await GroupRepository.delete(4, 'u1', group)).toBe(true)
+
+    const [del, history] = connection.query.mock.calls
+    expect(del[0]).toMatch(/DELETE FROM hotel_groups/)
+    expect(history[0]).toMatch(/INSERT INTO group_history[\s\S]*'deleted', 'hotel_groups'/)
+    expect(history[1]).toEqual([4, 4, JSON.stringify(group), 'u1'])
+    expect(connection.commit).toHaveBeenCalledOnce()
+  })
+
+  it('rolls the delete back when the history row fails', async () => {
+    connection.query
+      .mockResolvedValueOnce([{ affectedRows: 1 }])
+      .mockRejectedValueOnce(new Error('history insert failed'))
+
+    await expect(GroupRepository.delete(4, 'u1', group)).rejects.toThrow('history insert failed')
+    expect(connection.rollback).toHaveBeenCalledOnce()
+    expect(connection.commit).not.toHaveBeenCalled()
+  })
+
+  it('writes no history when there was no group to delete', async () => {
+    connection.query.mockResolvedValueOnce([{ affectedRows: 0 }])
+
+    expect(await GroupRepository.delete(4, 'u1', group)).toBe(false)
+    expect(connection.query).toHaveBeenCalledOnce()
+  })
+
+  it('a migration drops the cascade from group_history', () => {
+    const script = readFileSync(
+      join(
+        dirname(fileURLToPath(import.meta.url)),
+        '..',
+        '..',
+        'db-mysql',
+        'scripts',
+        '20261011_keep_group_history_on_delete.sql'
+      ),
+      'utf8'
+    )
+    expect(script).toContain('ALTER TABLE group_history DROP FOREIGN KEY group_history_ibfk_1')
+  })
+})