Plugins: create the settings collection instead of waiting for it forever

01a8fec fixed the advice that led operators into this, but advice is not a
guard: a stack still running PB_BOOTSTRAP=false gets no app_settings
collection on upgrade, and the plugin panel sits at 503 while the retry
loop reads a collection that does not exist.

The fix is not to soften the reading. A missing collection stays "not
ready" rather than "no plugins configured", because the alternative lets
the first save write a fresh document over settings the server merely
failed to find - the failure this whole line of work exists to prevent.
Instead the server now fixes the cause: on a missing collection it creates
that collection and reads again.

Three pieces:

bootstrap.EnsureCollection creates one named collection from the desired
schema if absent, and nothing else. Deliberately narrower than Run - no
field reconcile elsewhere, no super-admin - so it is safe to call on a
deployment that turned the full bootstrap off. It creates the collection
the server cannot start without, not the schema the operator declined.

The store tells a missing collection apart from an outage. A 404 from a
list means the collection itself is gone: an existing but empty one answers
200 with no items. That is tagged errNoCollection, which wraps errNotReady
so every write is still refused, and IsMissingCollection narrows it. The
distinction matters because the remedies are opposites - creating
collections against a flaky database is exactly the wrong reflex, and a
test pins that an outage does not trigger it.

loadPlugins acts on the tag once, then re-reads. Failing to create is
reported as the original read error rather than the repair's, so the log
names the real problem.

Six tests: the tag and its negative in internal/plugins, and three in
internal/api against a fake PocketBase covering the collection being
created exactly once, an existing collection not being recreated, and an
outage creating nothing.

Docs from 01a8fec are corrected in the same pass - they said the panel
would answer 503 forever, which is no longer true. They now say what still
depends on the bootstrap (every other collection and field) and what does
not (app_settings alone).

go build, go vet and go test ./... pass; compose files still parse. Not
verified: no Docker CLI here, so the repair has not been exercised against
a real PocketBase, only the fake.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Docker-AIO/.env.prod.example

@@ -18,10 +18,11 @@ DRIVERVAULT_SUPERADMIN_EMAIL=owner@example.com
 DRIVERVAULT_SUPERADMIN_PASSWORD=change-me-long-password
 DRIVERVAULT_SUPERADMIN_NAME=Administrator
 
-# Schema creation/reconcile on boot. Leave this true: a release can add a
-# collection the server needs (app_settings, which holds the plugin settings),
-# and a stack that skipped the bootstrap never gets it — the plugin panel then
-# answers 503 forever. Set false only for a database you know matches the release.
+# Schema creation/reconcile on boot. Leave this true: a release can add
+# collections or fields the server needs, and a stack that skips the bootstrap
+# never gets them. (The API Server creates app_settings, which holds the plugin
+# settings, on demand — but only that one.) Set false only for a database you
+# know already matches the release.
 PB_BOOTSTRAP=true
 
 # Allowed CORS origin(s) — match your public web URL / WEB_PORT.