refactor: pure env_file stack.env convention across all stacks

Every service now reads stack.env via env_file with container-exact var
names — no ${VAR} parse-time interpolation, no Portainer UI env vars
(except stacks/dev, kept on UI-env interpolation as documented exception).

- media: drop PUID/PGID/TZ env lines (env_file covers); resolve ${ROOT}
- foundry: secrets via env_file; FOUNDRY_PATCH_URLS -> CONTAINER_PATCH_URLS
- monitoring: HOMARR_SECRET_ENCRYPTION_KEY -> SECRET_ENCRYPTION_KEY
- notify: FRESHRSS_USER composed in stack.env; TZ via env_file
- owncloud: container-exact OWNCLOUD_*/MYSQL_* keys; runtime $$ healthcheck
- resume/famapp: composites (DATABASE_URL etc.) written out in stack.env
- authentik: container-exact keys; image tag pinned in compose
- notes: couchdb creds via env_file
- remote: gains stack.env (no secrets; convention completeness)
- CLAUDE.md: env convention, valhalla-lab registration-only note, correct
  on-host Portainer working-copy path (/config/portainer/compose/<id>)

Validated with docker compose config on valhalla for all 15 stacks.

stacks/famapp/stack.env

@@ -1,16 +1,21 @@
-# famapp stack secrets
-FAMAPP_IMAGE=ghcr.io/ginnoir/famapp:latest
-FAMAPP_PULL_POLICY=always
+# famapp stack secrets — injected into all services via env_file.
+# Var names are exactly what each container reads (no ${VAR} interpolation,
+# no Portainer UI env vars). POSTGRES_* (db) are embedded in DATABASE_URL
+# (app) — keep them in sync on rotation. MINIO_ROOT_* are shared by the app
+# and the minio server. Image tag is pinned in docker-compose.yml.
 RUN_MIGRATIONS=true
 LOG_LEVEL=info
 
 AUTH_URL=https://fam.ginnoir.com
-FAMAPP_DB_USER=famapp
-FAMAPP_DB_PASSWORD=a9a999d16dd5cdc521bb62eff331265d3c24
-FAMAPP_DB_NAME=famapp
 
-# famapp Auth.js session secret (mapped to the container's AUTH_SECRET)
-FAMAPP_AUTH_SECRET=CJsICgBs78YxxSdJfS8KU9Zn9k+QytRoVui9kVtuHtI=
+# postgres (db container) + the composed URL the app reads
+POSTGRES_USER=famapp
+POSTGRES_PASSWORD=a9a999d16dd5cdc521bb62eff331265d3c24
+POSTGRES_DB=famapp
+DATABASE_URL=postgres://famapp:a9a999d16dd5cdc521bb62eff331265d3c24@famapp-db:5432/famapp
+
+# famapp Auth.js session secret
+AUTH_SECRET=CJsICgBs78YxxSdJfS8KU9Zn9k+QytRoVui9kVtuHtI=
 
 # OIDC via Authentik (public URL through Caddy — no container dependency)
 AUTH_OIDC_ISSUER=https://auth.ginnoir.com/application/o/famapp/
@@ -25,9 +30,9 @@ NTFY_URL=https://ntfy.ginnoir.com
 NTFY_TOPIC=famapp
 
 # MinIO object storage (plant/container image uploads)
-famapp_MINIO_ROOT_USER=famapp
-famapp_MINIO_ROOT_PASSWORD=d0fet0th3x
-famapp_MINIO_BUCKET=garden
+MINIO_ROOT_USER=famapp
+MINIO_ROOT_PASSWORD=d0fet0th3x
+MINIO_BUCKET=garden
 
-famapp_OPENPLANTBOOK_CLIENT_ID=5JdQLab69RhVaF4er7b7D29BCrkf3fo3OEiDsOQa
-famapp_OPENPLANTBOOK_CLIENT_SECRET=kxPTrdQPAVta7sjVuIRf5EGIJ1fKvlMlqRSJpQtFxRftJhg7oeGnXzwH7ls6tluQLFUYVDYRMwISiAuKZGZLvkuJzUwFGCwhZw7UtW8OvcTGy4717WeNUinvuCDSsNXP
+OPENPLANTBOOK_CLIENT_ID=5JdQLab69RhVaF4er7b7D29BCrkf3fo3OEiDsOQa
+OPENPLANTBOOK_CLIENT_SECRET=kxPTrdQPAVta7sjVuIRf5EGIJ1fKvlMlqRSJpQtFxRftJhg7oeGnXzwH7ls6tluQLFUYVDYRMwISiAuKZGZLvkuJzUwFGCwhZw7UtW8OvcTGy4717WeNUinvuCDSsNXP