fix(immich): name containers underscore to match runtime lifecycle code

package.stop/start/restart broke ("no containers found" / "no such object
immich_postgres") because the runtime hardcodes the immich stack's container names
as immich_server/immich_postgres/immich_redis (underscore) across 8 files
(lifecycle, health, crash-recovery, ports, config). The migration had named the
containers by app_id (hyphen), mismatching all of it.

Root cause of the earlier failed attempt: container_name was nested under an
`extensions:` block, but `app.extensions` is serde(flatten) — container_name must
be a TOP-LEVEL app key to be read by compute_container_name. Fixed: set
container_name: immich_server / immich_postgres / immich_redis at top level, and
point DB_HOSTNAME/REDIS_HOSTNAME at the underscore aliases. App ids stay hyphen
(immich/immich-postgres/immich-redis) so the catalog identity (title+icon) holds.

Manifest-only change — container names now match existing runtime references, no
code edits to the 8 files. (Deriving stack containers from manifests instead of
hardcoded lists remains a north-star follow-up.)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/immich-postgres/manifest.yml

@@ -4,10 +4,11 @@ app:
   version: "14-vectorchord0.4.3-pgvectors0.2.0"
   description: Postgres (pgvecto.rs / vectorchord) backend for Immich.
 
-  # No container_name override: the container is named by app_id (immich-postgres),
-  # which is also its archy-net alias and the server's DB_HOSTNAME. (Overriding the
-  # name diverges from the orchestrator's app_id-based naming and spawns duplicate
-  # containers — mirror the btcpay stack, which names members by app_id.)
+  # Container named immich_postgres (underscore) to match the runtime's existing
+  # per-app references (lifecycle/health/crash-recovery/config) and serve as the
+  # server's DB_HOSTNAME alias. Top-level key → serde(flatten) → extensions →
+  # compute_container_name.
+  container_name: immich_postgres
 
   container:
     image: 146.59.87.168:3000/lfg2025/immich-postgres:14-vectorchord0.4.3-pgvectors0.2.0