fix(api): a read-side failure waits for its event instead of losing it

The Redis consumer used to leave a failed event pending and go on to the
next ones, retrying it only at the next start. With Mongo down for a
while, a later change of the same ticket was then projected first, and
the version check dropped the earlier one for good (a status change
could vanish from the read model), besides the read side lagging until
a restart.

Now a failed event is retried in place, waiting longer each time (up to
30 s), and the next one waits for it. Failures of the infrastructure
(Mongo, Redis, the network: isTransientError) wait as long as it takes,
so the read side catches up by itself; an event that keeps failing on
its own goes, after 5 attempts, to <stream>:dead with its error, so it
does not hold up the rest.

GET /api/health reports the way from write to read (events waiting in
the outbox, pending to be projected, set aside) and says `degraded`,
still with 200, when something is stuck.

Tried for real: with Mongo stopped, two status changes went in; the
first failed to project with ECONNREFUSED, and once Mongo was back the
ticket's history had both steps, in order, without restarting the API.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/10-futuro.md

@@ -132,3 +132,6 @@ Mucho trabajo para lo que aportan hoy; se pueden recuperar si alguien los necesi
   directo y con la hora.
 - Panel para clientes: un enlace de solo lectura, sin cuenta, con los bloques que elijan el propietario y los admins
   (flujo, sprint, releases, épicas, actividad); se renueva o se retira desde Configuración.
+- De escritura a lectura: si un evento no se puede proyectar, se reintenta en su sitio (el siguiente espera) hasta
+  que Mongo vuelve, sin reiniciar ni perder cambios; los que fallan por sí mismos se apartan a
+  `task-stream:events:dead`, y `GET /api/health` avisa de eventos atascados o apartados.