refactor(backend): Redis -> Memcached

compose.staging.yml

@@ -87,16 +87,17 @@ services:
         restart: unless-stopped
 
     caching:
-        image: redis:6.2-alpine
+        image: memcached
         restart: always
         ports:
-            - '6379:6379'
-        command: redis-server --save 20 1 --loglevel warning
-        volumes:
-            - dwengo_cache:/data
+            - '11211:11211'
+        command:
+            - --conn-limit=1024
+            - --memory-limit=2048
+            - -I 128m
+            - --threads=4
 
 volumes:
     dwengo_grafana_data:
     dwengo_loki_data:
     dwengo_postgres_data:
-    dwengo_cache: