Add 24-hour time format option for timestamps

All timestamps across the dashboard (runs, logs, etc.) are currently displayed in 12-hour AM/PM format. This is confusing for users in regions where 24h is the norm, most of Europe and large parts of the world never use AM/PM in daily life.

Current: May 5, 2026, 10:53:28 AM Expected: May 5, 2026, 10:53:28

Suggestion: Either automatically respect the user's browser/system locale for time formatting, or add a simple 12h / 24h toggle in user preferences.

Small change, but makes the product feel native to non-US users.