Bump remaining apps: major version slots and infrastructure

New version slots (major version jumps):
- gitea: 1.24.3 -> 28.2.0 (slot 1 -> 28)
- ghost: 5.130.6 -> 6.72.0 (slot 5 -> 6)
- formbricks: 3.6.0 -> 6.1.0 (slot 3 -> 6)
- mattermost: 10.8.1 -> 12.0.1 (slot 10 -> 12)
- zulip: 9.4 -> 12.3 (slot 9 -> 12)
- immich: 1.135.3 -> 3.3.5 (slot 1 -> 3)
- openproject: 16.1.1 -> 17.9.3 (slot 16 -> 17)
- listmonk: 5.0.3 -> 6.1.0 (slot 5 -> 6)
- discourse: 3.5.3 -> 2026.10.0 (slot 3 -> 2026, calver)

Same-slot large bumps:
- vllm: 0.9.2 -> 0.32.0
- longhorn: v1.8.1 -> v1.13.0

Infrastructure:
- cert-manager: v1.17.2 -> v1.21.2
- coredns: v1.12.0 -> v1.14.7
- externaldns: v0.13.4 -> v0.23.0
- metallb: v0.15.0 -> v0.16.1
- mysql: 9.1.0 -> 9.7.4
- node-feature-discovery: v0.17.3 -> v0.20.1
- nvidia-device-plugin: v0.17.1 -> v0.20.1

discourse/versions/2026/manifest.yaml

@@ -0,0 +1,39 @@
+version: 2026.10.0
+requires:
+- name: postgres
+- name: redis
+- name: smtp
+defaultConfig:
+  namespace: discourse
+  storage: 2Gi
+  adminEmail: '{{ .operator.email }}'
+  adminUsername: admin
+  siteName: Community
+  domain: discourse.{{ .cloud.domain }}
+  db:
+    host: '{{ .apps.postgres.host }}'
+    port: '{{ .apps.postgres.port }}'
+    name: discourse
+    user: discourse
+  redis:
+    host: '{{ .apps.redis.host }}'
+  smtp:
+    enabled: false
+    host: '{{ .apps.smtp.host }}'
+    port: '{{ .apps.smtp.port }}'
+    user: '{{ .apps.smtp.user }}'
+    from: '{{ .apps.smtp.from }}'
+    tls: '{{ .apps.smtp.tls }}'
+    startTls: '{{ .apps.smtp.startTls }}'
+defaultSecrets:
+- key: adminPassword
+- key: secretKeyBase
+  default: '{{ random.Hex 32 }}'
+- key: smtpPassword
+- key: dbPassword
+- key: dbUrl
+  default: postgres://{{ .app.db.user }}:{{ .secrets.dbPassword }}@{{ .app.db.host
+    }}:{{ .app.db.port }}/{{ .app.db.name }}?sslmode=disable
+requiredSecrets:
+- postgres.password
+- redis.password