fix(rabbitmq): raise default resources preset to u1.nano - #3936

What this PR does

Raises the RabbitMQ default resource preset from t1.nano (128Mi memory) to u1.nano (1Gi memory). An explicit t1.nano remains valid, and existing application CRs that already persist resourcesPreset: t1.nano are not resized automatically.

The original default-sized RabbitMQ 4.2 pod on Cozystack 1.6.1 was OOMKilled with exit 137, reached 10 restarts, and never became Ready. A temporary u1.nano canary reached 3/3 Ready with zero restarts; its working-set snapshots were 114–121Mi. The canary and its storage were removed after validation.

The values, generated schema, ApplicationDefinition, typed API, and README use the same default. Tests cover the new default, an explicit legacy override, and explicit resources.

Validation:

• helm unittest packages/apps/rabbitmq: 3/3 passed.
• make -C packages/apps/rabbitmq generate: no diff.
• Provider counterpart: fix(rabbitmq): default resources_preset to u1.nano terraform-provider-cozystack#34.

Screenshots

Not a UI change.

Downstream repositories

The default is restated by the Terraform provider, so the linked provider PR updates it and documents the state-plan implication. No other trigger-map entry matches this diff.

• No downstream repository is affected by this change
• cozystack/website - follow-up:
• cozystack/terraform-provider-cozystack - follow-up: fix(rabbitmq): default resources_preset to u1.nano terraform-provider-cozystack#34
• cozystack/ansible-cozystack - follow-up:
• cozystack/ccp - follow-up:
• cozystack/talm - follow-up:
• cozystack/cozyhr - follow-up:
• cozystack/cozy-proxy - follow-up:
• cozystack/cozystack-telemetry-server - follow-up:
• cozystack/external-apps-example - follow-up:
• cozystack/examples - follow-up:

Release note

fix(rabbitmq): raise the default resource preset from t1.nano to u1.nano to prevent default-sized brokers from exhausting memory