Docker-AIO: one image per database

Dockerfile builds warp-aio on SQLite, Dockerfile.PocketBase builds
warp-aio-pocketbase and Dockerfile.PostgreSQL builds warp-aio-postgresql
with PostgreSQL bundled. The database driver and connection string now
come from the image, so the SQLite and PocketBase images no longer carry
PostgreSQL (103 MB instead of 149 MB). The AIO compose files point at
their own Dockerfile and image, and the entrypoint refuses to start an
embedded PostgreSQL in an image that has none.

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

Docker-AIO/.env.example

@@ -9,8 +9,8 @@
 # An empty value means the built-in default, given in the comment above it.
 # Every homeserver setting is described in docs/configuration.md.
 #
-# Set by the compose files, not here: the database driver and connection
-# string (each file is one database), the listen addresses, the signing key
+# Set by the image, not here: the database driver and connection string
+# (each Dockerfile is one database), the listen addresses, the signing key
 # and media paths inside /data, the address the admin panel and web client
 # reach the homeserver on, and whether the bundled PostgreSQL runs.
 
@@ -21,8 +21,9 @@ WARP_PORT=8008
 WARP_ADMIN_PORT=8009
 WARP_WEB_PORT=8080
 
-# The *.prod.yml files pull $WARP_REGISTRY/warp-aio at this tag. Pin a
-# release in production.
+# The *.prod.yml files pull $WARP_REGISTRY/warp-aio (SQLite),
+# warp-aio-pocketbase or warp-aio-postgresql at this tag. Pin a release in
+# production.
 WARP_REGISTRY=ghcr.io/dariuszjaniak
 WARP_VERSION=latest