build(deployment): use sibling repos as docker build context

backend/.env.sample

@@ -11,7 +11,7 @@ DJANGO_ALLOWED_HOSTS=
 POSTGRES_DB=app_db
 POSTGRES_USER=app_user
 POSTGRES_PASSWORD=app_password
-POSTGRES_HOST=localhost
+POSTGRES_HOST=db
 POSTGRES_PORT=5432
 
 # CORS / CSRF
@@ -30,11 +30,11 @@ JWT_ALGORITHM=HS256
 
 # Redis / Celery
 REDIS_URL=redis://redis:6379/0
-REDIS_HOST=127.0.0.1
+REDIS_HOST=redis
 REDIS_PORT=6379
 REDIS_PASSWORD=
-CELERY_BROKER_URL=
-CELERY_RESULT_BACKEND=
+CELERY_BROKER_URL=redis://redis:6379/0
+CELERY_RESULT_BACKEND=redis://redis:6379/0
 
 # Timzone / Language
 LANGUAGE_CODE=en-us