[MDS-6802] - Tier History Date Fix

[matbusby-fw]

Objective

MDS-6802

Description

This PR resolves an issue in the now tier History Modal where timestamps were displaying an incorrect time, shifted by the local timezone offset.
Root Cause:
The backend HistoryMixin (which provides the history trail) was exposing UTC timestamps in its JSON payload without providing the timezone offset suffix. The frontend received 2026-04-08T20:42:00 and parsed it locally, incorrectly resolving it as 8:42 PM local time rather than extracting the local equivalent from UTC.

Fix:
Wrapped the updated_at mapping in models_mixins.py with the existing dt_to_str helper. This ensures the output string adheres to ISO8601 formatting and includes the +00:00 UTC offset indicator, allowing moment.js to parse it correctly into the user's local timezone.

Side Effects Analysis:
The HistoryMixin is also utilized by Tailings Storage Facilities (TSFs) and Dams.

• Why it's safe: The frontend components for TSFs and Dams (TailingsDiffModal.tsx and DiffTable.tsx) run the updated_at API output through a formatDate helper rather than formatDateTime. The formatDate helper forces strict parsing against the "YYYY-MM-DD" format. This hard-strips out the time and ignores the new +00:00 suffix. As a result, there are zero visual side effects on existing TSF or Dam history tables.

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Manual Test Plan

• Log in as a Core user.
• Navigate to an active Notice of Work (NOW) application.
• Update the tier allocation to trigger a new entry in the tier history logs.
• Open the tier history modal.
• Verify that the recorded timestamp accurately reflects your current local time, completely eliminating the 6-hour offset gap.
• Navigate to the Tailings Storage Facility (TSF) tab of a mine that has TSF history.
• Open the TSF history/diff modal.
• Verify the history table renders without errors and the date accurately falls back to MMM DD YYYY (e.g., Apr 08 2026) without displaying the time.

[sonarqubecloud]

Quality Gate passed for 'bcgov-sonarcloud_mds_core-api'

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud