Fix: make refresh-materialized-view log dynamic with interval and time zone

[YashSejani]

Description This PR fixes an incorrect log message in the Celery initialization code.
Previously, the log line hardcoded “Scheduling refresh materialized view every night at 1am CDT”,
which was misleading because the refresh interval is configurable and not tied to a specific timezone.

This PR updates the message to:

• Dynamically show the configured refresh interval (mat_views_interval days)
• Display the system timezone
• Log the next expected refresh time relative to Augur startup

This improves clarity and accuracy for users running Augur in different environments.

Fixes #3360

Notes for Reviewers

• The job still runs based on mat_views_interval (default from config).
• Timezone is derived dynamically from the system settings.
• Tested locally to confirm the new log output prints correctly.

Signed commits

• [x] Yes, I signed my commits.

[MoralCode]

Also be aware that this PR, #3368, and #3370 are all solving the same issue, and only one of them can be merged.