upstream(immich): document concurrent app+db restart update_config fix

cc-ci-plan/upstream/immich.md

@@ -24,6 +24,15 @@
   image to `14-vectorchord0.4.3-pgvectors0.3.0@sha256:87c050465fb969a68c7ac23e375e21f4c95cfacd0edce5fa1bc31e63b7891891`
   (same PG14 + VectorChord 0.4.3, newer pgvectors 0.2.0→0.3.0). Digest verified via
   `docker buildx imagetools inspect` on cc-ci (2026-06-12).
+- **Concurrent app+database restart needs `update_config: failure_action: continue` on the app service.**
+  When the recipe version label changes (bumping `coop-cloud.${STACK_NAME}.version`) AND the database
+  image changes in the same deploy, both services update simultaneously. The app container starts and
+  immediately tries TypeORM migrations against a still-restarting database → TypeORM connection fails →
+  app process crashes → task FAILED → Docker Swarm sets `UpdateStatus='paused'` (default
+  `failure_action: pause`). Fix: set `update_config: failure_action: continue` on the app service.
+  With `continue`, Docker Swarm records the update as `completed` and Docker's `restart_policy` retries
+  the app container; the database finishes restarting in ~15-20s and the app connects successfully.
+  This is also in the recipe as of PR #2.
 - **VectorChord DB backup/restore needs the search_path sed.** A plain `pg_dump` of the
   VectorChord/pgvecto.rs DB emits `SELECT pg_catalog.set_config('search_path', '', false);`. Importing
   that as-is leaves the vector/vchord type + operator references unresolvable, so the first such