Add persistent NWS severe weather alerts and automation triggers

[mot-yelraf]

Summary

Add NWS severe-weather warnings and watches for a verified US Astral location when US NWS is selected. A new Severe Weather automation condition supports existing actors, with detailed Alert/Notify messages and persistent once-per-event tracking. Dashboard forecast content and its Caelus button turn orange during active events; Caelus shows the detailed event message.

Weather Alerts persist until dismissed and replay when a dashboard connects, fixing messages lost during application startup. Explicit disable/save followed by enable/save rearms an existing automation; ordinary saves, restarts, dismissals, and NWS updates retain deduplication. Alert messages use orange backgrounds and black text, and condition remove buttons align on the right. Version: v0.26.271.7.

Verification

• User verified the changes on their installation.
• macOS, Python 3.13.9: focused weather, automation, switch, email, route, database migration, and compile tests: 384 passed, 1 skipped.
• npm run validate:pr: 50 passed using host-side Playwright/Chromium dashboard and automation checks.
• git diff --check.
• Automated checks use mocked NWS traffic, switch actors, and email delivery with real isolated SQLite persistence. No live MQTT broker or direct hardware is required.

Contributor checklist

• This pull request is focused on one logical change.
• I added or updated tests for behavior changes.
• I updated the canonical documentation when behavior or configuration changed.
• I did not commit credentials, private runtime configuration, databases, or logs.
• I preserved compatibility-sensitive MQTT, settings, switch identity, and persistence behavior, or documented an intentional break.

Maintainer verification

• Required remote checks pass.
• npm run validate:pr passes on a trusted host when the change can affect rendered UI behavior.
• Hardware-, broker-, onboarding-, and platform-specific behavior not covered remotely is recorded below.

Residual risk or unverified areas

Agent testing did not exercise live NWS events, physical switch hardware, SMTP delivery, or onboarding. The existing email queue is in memory, so a crash after enqueue but before delivery can lose that email. Earlier weather trigger receipts without saved Alert payloads cannot be replayed; explicitly re-enabling the automation now allows a fresh trigger.