chore(deps): pin dependencies

resources/chaosknoten/tickets/docker_compose/compose.yaml.j2

@@ -1,7 +1,7 @@
 ---
 services:
   database:
-    image: docker.io/library/postgres:15-alpine
+    image: docker.io/library/postgres:15-alpine@sha256:6bd113a3de3274beda0f056ebf0d75cf060dc4a493b72bea6f9d810dce63f897
     environment:
       - "POSTGRES_USER=pretix"
       - "POSTGRES_PASSWORD={{ secret__pretix_db_password }}"
@@ -13,7 +13,7 @@ services:
     restart: unless-stopped
   
   redis:
-    image: docker.io/library/redis:7
+    image: docker.io/library/redis:7@sha256:a9cc41d6d01da2aa26c219e4f99ecbeead955a7b656c1c499cce8922311b2514
     ports:
       - "6379:6379"
     volumes:
@@ -25,7 +25,7 @@ services:
       backend:
 
   pretix:
-    image: docker.io/pretix/standalone:2024.8
+    image: docker.io/pretix/standalone:2024.8@sha256:110bac37efa5f736227f158f38e421ed738d03dccc274dfb415b258ab0f75cfe
     command: ["all"]
     ports:
       - "8345:80"