PocketBase as a standalone database server

The pocketbase driver no longer embeds PocketBase: Warp keeps its data as
PocketBase collections on a server of its own and reaches it only through
the REST API, the way the postgres driver reaches PostgreSQL.
database.connection_string is the server's URL, and Warp signs in as the
superuser in WARP_PB_SUPERUSER_EMAIL / WARP_PB_SUPERUSER_PASSWORD (or a
WARP_PB_SUPERUSER_FILE of the two).

Every SQL table is a superuser-only collection of the same name and
columns, created by warp migrate. Reads go through PocketBase's SQL
endpoint with the SQL drivers' queries, via a read-only database/sql
driver that inlines arguments, moves long ones into warp_params and pages
past 1000 rows. Writes are record operations in batch requests under one
write lock in the Warp process. Media is a protected file field in
warp_media, local or in the S3 bucket Warp writes into PocketBase's
settings. Search matches word prefixes with LIKE. The storage tests run
against an in-process PocketBase and pass as on SQLite.

Docker: the PocketBase stacks get a pocketbase service running
tajniak81/pocketbase-docker-root (WARP_PB_IMAGE), with a pb-data volume
and its admin UI on loopback; the AIO images run that PocketBase binary
as a process beside the homeserver, making up a superuser when none is
set. The .env examples, READMEs, docs and warp.yaml.example follow.

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

Docker/.env.pocketbase.example

@@ -21,11 +21,31 @@ WARP_PORT=8008
 WARP_ADMIN_PORT=8009
 WARP_WEB_PORT=8080
 
+# The PocketBase image; any PocketBase 0.40 or later answers the same.
+WARP_PB_IMAGE=tajniak81/pocketbase-docker-root:latest
+
+# PocketBase's port, for its admin UI at http://localhost:8070/_/. It is
+# on loopback unless the bind address says otherwise; put the UI behind a
+# reverse proxy before binding it to 0.0.0.0.
+WARP_PB_BIND=127.0.0.1
+WARP_PB_PORT=8070
+
+# The PocketBase superuser the homeserver signs in as, and so can you, in
+# the admin UI. The pocketbase container creates it on its first start and
+# leaves it alone after that: to change the password, change it in the
+# admin UI first, then here. It needs 8 characters or more.
+WARP_PB_SUPERUSER_EMAIL=admin@example.org
+WARP_PB_SUPERUSER_PASSWORD=change-me-now
+
 # Where the data lives. Empty keeps the named volume in brackets; a
 # host path (starting with . or /) bind-mounts that directory instead.
-# The homeserver runs as UID 10001, so its directory must be writable by it.
-# The homeserver's /data (warp-data).
+# The homeserver runs as UID 10001, so its directory must be writable by
+# it; PocketBase runs as root.
+# The homeserver's /data (warp-data): its signing key.
 WARP_DATA_VOLUME=
+# PocketBase's pb_data (pb-data): the database, and media unless it is
+# in S3.
+WARP_PB_DATA_VOLUME=
 
 # ------------------------------------------------------------ homeserver