feat: one generic image, with installed modules in installation-owned storage (ADR 0048)

The production image now contains zero feature modules and is the same for every
installation. Installed modules live in module storage that one Core resolver
selects from EKKLESIA_MODULES_DIR: the checkout's modules/ when unset, an
absolute path that must exist when set (/var/lib/ekklesia/modules in the image).
A relative, blank, missing, or unreadable configured directory fails closed with
a sanitized error that never contains the value.

- Host configuration reads EKKLESIA_MODULES_DIR. The API, migration plan, apply
  and validate, module validation, module enablement, and Doctor all resolve it
  the same way; the test-only API override still takes precedence.
- Doctor receives Core's migrations directory explicitly instead of deriving it
  from the modules directory's parent.
- The migration runner retains and reports the applied history of a module that
  is not installed, and plans and applies Core's and present modules' migrations
  around it. Core's history and every installed module's history stay strict: a
  missing or changed applied migration, or a downgrade, still fails. No down
  migrations, no data deletion.
- deploy/Dockerfile copies no module and installs nothing for the module
  template; .dockerignore excludes modules/ and the build refuses a context that
  contains it; the runtime has an empty root-owned /var/lib/ekklesia/modules and
  sets EKKLESIA_MODULES_DIR.
- deploy/compose.yaml bind-mounts EKKLESIA_MODULES_HOST_DIR read-only into api
  and migrate, with create_host_path disabled.
- scripts/check-image.sh proves the image holds no modules and that a populated
  modules/ directory leaves its runtime file system identical; CI runs it.
- The split deploy smoke now uses the same generic image: it boots with no
  modules, installs a self-contained test module packaged from the template
  (test-only), migrates and restarts, removes it (Core runs, planning reports the
  retained history, data survives), and restores it with its data.

Docs: deploy README (module storage, install/update/remove/restore, the runtime
modules target), .env.example, API configuration, module development guide,
testing, workflow, security, and the architecture overview.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

deploy/env/compose.env.example

@@ -15,6 +15,12 @@ EKKLESIA_IMAGE=
 EKKLESIA_ENV_DIR=/etc/ekklesia
 EKKLESIA_TLS_DIR=/etc/ekklesia/tls
 
+# Installed modules (ADR 0048): the host directory mounted read-only into `api` and `migrate` at
+# /var/lib/ekklesia/modules. It must already exist; Compose never creates it. Create it once, owned
+# by root, before the first `up`:
+#   sudo install -d -o root -g root -m 755 /var/lib/ekklesia/modules
+# EKKLESIA_MODULES_HOST_DIR=/var/lib/ekklesia/modules
+
 # --- compose.proxy.yaml ---------------------------------------------------------------------------
 # The Ekklesia hostname and the storage hostname (signed object URLs). In the default same-origin
 # topology (Caddyfile.example) EKKLESIA_HOSTNAME serves the Dashboard, the API, and displays.

deploy/env/ekklesia.env.example

@@ -6,9 +6,14 @@
 # Never commit the filled-in file. Generate secrets with scripts/gen-secrets.sh, and the database CA
 # line with scripts/init-tls.sh.
 #
-# The image already sets NODE_ENV=production, EKKLESIA_API_HOST=0.0.0.0, and EKKLESIA_API_PORT=3000.
-# Compose sets NODE_EXTRA_CA_CERTS. The proxy overlay sets the three EKKLESIA_CLIENT_ADDRESS_*
-# variables. None of those belong here.
+# The image already sets NODE_ENV=production, EKKLESIA_API_HOST=0.0.0.0, EKKLESIA_API_PORT=3000, and
+# EKKLESIA_MODULES_DIR=/var/lib/ekklesia/modules. Compose sets NODE_EXTRA_CA_CERTS and mounts module
+# storage at that path. The proxy overlay sets the three EKKLESIA_CLIENT_ADDRESS_* variables. None of
+# those belong here.
+#
+# Installed modules (ADR 0048) are read from EKKLESIA_MODULES_DIR, which must name the mounted
+# directory. Move the host directory with EKKLESIA_MODULES_HOST_DIR in deploy/.env instead.
+# EKKLESIA_MODULES_DIR=/var/lib/ekklesia/modules
 #
 # Values that are part of the reference topology are filled in; everything installation-specific is
 # blank. Full reference: docs/development/api.md#required-configuration.