chore: merge upstream main into the upgrade branch

The branch predated the official-image migration (coop-cloud/discourse#16), so its
merge-base was 0.8.1+3.5.0 and the PR's file list re-showed that migration's changes
as if this PR introduced them. The branch TREE already matched upstream; only its
history lacked those commits. Recording the merge leaves the PR's diff as what it
actually changes: app 3.5.3 -> 2026.7.1 and redis 7.4-alpine -> 8.10-alpine.

Conflict in compose.yml resolved in favour of the branch (both sides edited the same
image lines; the branch already carries upstream's official-image switch plus the
version bumps). Resulting tree is byte-identical to the pre-merge branch tree.

compose.yml

@@ -3,7 +3,7 @@ version: "3.8"
 
 services:
   app:
-    image: discourse/discourse:3.5.3
+    image: discourse/discourse:2026.7.1
     networks:
       - proxy
       - internal
@@ -116,7 +116,7 @@ services:
         backupbot.restore.post-hook: "/pg_backup.sh restore"
 
   redis:
-    image: redis:7.4-alpine
+    image: redis:8.10-alpine
     networks:
       - internal
     volumes:

release/next

@@ -2,6 +2,8 @@ This release switches from the bitnami image to the official discourse/discourse
 image. Some env vars need to be renamed for this migration; everything else
 should happen automatically.
 
+** WARNING A: renaming env vars
+
 Rename these in your app's .env (the values carry over):
 
   DISCOURSE_SMTP_HOST     --> DISCOURSE_SMTP_ADDRESS
@@ -9,7 +11,17 @@ Rename these in your app's .env (the values carry over):
   DISCOURSE_SMTP_AUTH     --> DISCOURSE_SMTP_AUTHENTICATION
   DISCOURSE_SMTP_PROTOCOL --> DISCOURSE_SMTP_ENABLE_START_TLS (takes a boolean true/false, not the old tls/ssl value, so translate it rather than copying it straight across)
 
-WARNING: if your deployment's database has an "install user" other than `postgres`
+** WARNING B: undeploy before deploy 
+
+it is necessary to `abra app undeploy` your old discourse app before deploying this version. otherwise the database will get killed and be in a bad state before the migration. 
+this was a non-fatal error in testing, but still a huge pain. 
+
+`abra app undeploy YOURDOMAIN` # cleaning stops your discourse
+`abra app deploy YOURDOMAIN` # with the new version 
+
+** WARNING C: install user
+
+if your deployment's database has an "install user" other than `postgres`
 (some older deployments do), you must set the POSTGRES_USER env var in your .env
 for this migration, otherwise the postgres upgrade aborts with an install-user
 mismatch.