Configurable Sentry error reporting for Hive

Hive now reports errors to Sentry when configured. Setting a SENTRY_DSN (optionally with SENTRY_ENVIRONMENT and SENTRY_RELEASE) causes the application to forward Phoenix request errors, LiveView errors, Logger errors, Oban job failures (including retry attempts by default), and scheduled-job check-ins to Sentry. The Oban behavior can be tuned through SENTRY_OBAN_CAPTURE_ERRORS and SENTRY_OBAN_CRON_MONITORING, and SENTRY_OBAN_REPORT_RETRIES=false limits reporting to jobs that have exhausted all attempts. Expected route and transport noise is filtered before events leave the app. Deployments without SENTRY_DSN keep their previous behavior, so Sentry only activates when an operator opts in, matching the existing Atlas integration.