[UX] Oracle data timestamps show UTC instead of local time

## Description
Oracle page shows timestamps in UTC format, which may confuse users in different timezones.

## Current behavior
Timestamps display as UTC (e.g., 2026-08-25T10:00:00Z).

## Expected behavior
Convert to user's local timezone or show timezone indicator.

## Files
- components/oracle/OracleDataWidget.tsx

## Impact
Users may misinterpret when data was last updated.