chore: upgrade to 1.3.0+6.43.1-alpine

Upgrade ghost image from 6.21.2-alpine to 6.43.1-alpine (same major, no breaking changes).
Keep MySQL at 8.0 — Ghost only supports MySQL 8 in production; MySQL 9 is not supported.

compose.yml

@@ -1,6 +1,6 @@
 services:
   app:
-    image: ghost:6.21.2-alpine
+    image: ghost:6.43.1-alpine
     environment:
       # see https://ghost.org/docs/config/#configuration-options
       database__client: mysql
@@ -51,7 +51,7 @@ services:
         - "traefik.http.middlewares.${STACK_NAME}-redirect.redirectscheme.permanent=true"
         - "backupbot.backup=true"
         - "backupbot.backup.path=/var/lib/ghost/content"
-        - "coop-cloud.${STACK_NAME}.version=1.2.0+6.21.2-alpine"
+        - "coop-cloud.${STACK_NAME}.version=1.3.0+6.43.1-alpine"
     healthcheck:
       test: ["CMD", "wget", "--header=X-Forwarded-Proto: https", "--spider", "-q", "http://localhost:2368/ghost/api/admin/site"]
       interval: 30s

release/1.3.0+6.43.1-alpine

@@ -0,0 +1 @@
+upgrade ghost image from 6.21.2-alpine to 6.43.1-alpine (within-major, no breaking changes)