The charm had no ``hooks/init``, so Carbone started in its default
stateless mode: no Studio, no template management, and ``CARBONE_BIND``
defaulting to ``127.0.0.1`` (unreachable behind the web-proxy).
Add ``hooks/init`` to:
- bind on ``0.0.0.0`` so the ``web-proxy`` can reach the service ;
- serve the Studio and ``/carbone-studio.js`` (``CARBONE_STUDIO``) ;
- enable stateful template management (``CARBONE_TEMPLATE_MANAGEMENT``):
stable 64-bit template IDs, versioning and the ``/template`` endpoints ;
- align the datastore/configstore ownership on the unprivileged
``carbone`` image user, otherwise the container crash-loops with
``EACCES`` on ``/app/config/config.json``.
Persist ``/app/config`` as a ``config-resources`` and set a
``docker-compose.stop_grace_period`` of 200s: Carbone flushes its
template metadata on graceful shutdown, and Docker's 10s default would
SIGKILL it and lose templates on redeploy. Flush metadata every
5 minutes to shrink the hard-crash window.
Bump the image to ``full-5.15.1`` and add a local ``basic-deploy`` test.
Verified locally: ``/status`` 200, ``/carbone-studio.js`` 200,
``GET /templates`` 200, template upload with versioning plus render
from the stable template ID, and metadata survival across a container
recreation.
