Adds Pushover as a new notification channel, allowing users to receive
push notifications on their devices via the Pushover API.
Backend: provider, type registration, validation, service wiring
Frontend: form UI with app token and user key fields, validation, i18n
Tests: full unit test suite (15 tests, 100% coverage on provider)
Closes#3445
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
egeoztassandClaude Opus 4.6
97353bc7d2