v2.9.1 pre-release: MQTT publishing for non-admin users

Experimental fix for #117.
This is a pre-release for testing, not a replacement for stable v2.9.0.

Changes

• Admin users keep the existing direct mqtt.publish path.
• Non-admin users can publish through an administrator-installed automation by setting mqtt.publish_automation.
• The relay handles timer snapshots, state markers, and all timer events. Both MQTT compatibility formats remain supported.
• Added a relay picker under Timer storage in the visual editor.
• Permission errors pause further writes instead of repeatedly calling the denied action. Missing relay configuration produces one setup warning per card.
• Non-admin users without a relay keep direct publishing on known HA versions before 2026.10.
• No automatic local-storage fallback and no admin tokens in the browser. Adding the relay setting preserves existing automatic namespaces and pinned IDs.

Required setup

Installing the card update alone is not enough for non-admin users on HA 2026.10+.

1. Install v2.9.1 from HACS's redownload/version selector (enable pre-release versions if necessary), or download the attached simple-timer-card.js.

2. As an administrator, create an automation using this example. Set its three topics to match your existing card and sensor, and leave it enabled.

3. Add its actual entity ID to the card's existing MQTT configuration:

   mqtt:
     sensor_entity: sensor.simple_timer_store
     publish_automation: automation.simple_timer_card_mqtt_relay

   Keep existing custom topics and other MQTT settings. HA may assign the automation a different entity ID.

4. Fully reload the dashboard on each testing device.

The relay fixes destinations and retain flags server-side and validates payload shape and size inside its actions. Do not move these checks or policy variables to top-level conditions/variables.

Full setup and test checklist

Validation and limitations

• Build and 126 targeted regression tests passed.
• 17 validator checks passed in Home Assistant's template renderer, including acceptance at exactly 262144 JSON characters and rejection at 262145.
• Not yet verified end-to-end with a real non-admin account. Please test preset/custom starts, pause/resume/cancel, expiry events, shared-sensor updates, and cross-device synchronization.
• A successful automation trigger is not proof of successful MQTT delivery. Check the automation trace, HA logs, and shared sensor.
• The relay depends on HA's automation context behavior. A plain script wrapper is not equivalent. The existing best-effort MQTT reconciliation and notification limitations still apply.

Please report results on #117, including your HA version and any relevant errors, without credentials or private payloads.