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-redis/manifest.yml

@@ -4,7 +4,9 @@ app:
   version: "7-alpine"
   description: Valkey (Redis-compatible) cache for Immich.
 
-  # Named by app_id (immich-redis) = archy-net alias = server's REDIS_HOSTNAME.
+  # Container named immich_redis (underscore) to match runtime per-app references
+  # and serve as the server's REDIS_HOSTNAME alias on archy-net.
+  container_name: immich_redis
 
   container:
     image: 146.59.87.168:3000/lfg2025/valkey:7-alpine