wger: revert 2.6 -> 2.3 (2.6 needs a full DB config the template cannot supply)

wger 2.6 crash-loops on a fresh deploy. Its settings/main.py reads the whole
DJANGO_DB_* set unconditionally -- even when the engine is sqlite:

  ImproperlyConfigured: Set the DJANGO_DB_DATABASE environment variable
  ...then, once that was supplied:
  ImproperlyConfigured: Set the DJANGO_DB_USER environment variable

Satisfying it means either stuffing in dummy USER/PASSWORD/HOST/PORT values that
the sqlite backend ignores, or giving wger a real Postgres sidecar. The first is
a hack, the second is compose restructuring -- both outside this campaign's
allowed-fix set.

Reverted to the previously shipped 2.3. NOTE: the interim DJANGO_DB_DATABASE
line added earlier in this campaign is reverted TOO, deliberately -- on 2.3 the
sqlite path came from wger's own default, and pinning a different explicit path
would have pointed an existing customer's wger at an empty database.

Campaign 7 catalog sweep.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Nn3VgQk9iwEGgyx6QJ2NvE

templates/wger/docker-compose.yml

@@ -9,17 +9,13 @@
 
 services:
   wger:
-    image: wger/server:2.6
+    image: wger/server:2.3
     container_name: wger
     restart: unless-stopped
     environment:
       - TZ=Europe/Budapest
       - SECRET_KEY=${SECRET_KEY}
       - DJANGO_DB_ENGINE=django.db.backends.sqlite3
-      # A wger 2.6 már NEM ad alapértelmezést ehhez, sqlite esetén sem: enélkül
-      # induláskor elszáll ("Set the DJANGO_DB_DATABASE environment variable").
-      # A wger_data kötetre mutat, hogy az adatbázis újratelepítést is túléljen.
-      - DJANGO_DB_DATABASE=/home/wger/db/database.sqlite
       - SITE_URL=https://${SUBDOMAIN}.${DOMAIN}
     volumes:
       - wger_data:/home/wger/db