Run locally like the sibling apps: fixed ports, the pod provider in Docker, the app outside

Festipod now follows the local convention of welcometomyplace, mutual-aid.app
and portejunes: one fixed port pair per app (Festipod defaults: backend 3005,
app 4005; pod provider 3000/5000), overridable in backend/.env and .env.
`make start` runs docker-compose-dev.yml (the local pod provider from images,
Fuseki, Redis, mailcatcher, Arena); the backend and the app run outside Docker
with `cd backend && pnpm dev` and `pnpm dev`. pnpm stays the package manager.

The old docker-compose.yml, which containerized Festipod's own frontend and
backend and could not reach the host's Fuseki and Redis, is gone; portless is
dropped from the dev script, since the backend declares a single OIDC redirect
URI. The local backend runs without a Redis cache, as the sibling apps do. The
e2e suites and validate read the app, backend and pod provider URLs from the
env files instead of hardcoding them.

The deployment and local cookbook leaves record the traps met while resetting
datasets: a dataset re-created under the same name needs a Fuseki restart
(ClosedException otherwise), the anonymous WebACL probe at boot is expected,
and a change of the backend's URL leaves persistent accounts with a
participations collection the new app identity cannot control.

docker-compose.coolify.yml

@@ -30,6 +30,9 @@
 #      disk — remove `databases/<main>`, `databases/<main>Acl`, `databases/<main>Mirror` and
 #      `configuration/<main>.ttl` under the Fuseki base too, or a dataset created again under
 #      the same name reopens the old data;
+#      Fuseki then keeps the closed storage of the deleted dataset: re-creating one under the
+#      SAME name fails every query with `ClosedException: already closed` until Fuseki restarts
+#      (the shared one, on the test server) — or set new MAIN_DATASET / SETTINGS_DATASET names;
 #   2. empty this stack's Redis (the `redis-data` volume): its cache outlives the datasets and
 #      would keep serving the old app actor, keys and access needs;
 #   3. redeploy.