Fix filter not respected when downloading visualizer-affected card from dashboard

[andsalves]

Closes #71638

Description

Fixes dashboard XLSX downloads for multi-source visualizer dashcards so applied dashboard filters are preserved in the download request.

The dashboard-card export endpoint already accepts parameters, but visualizer dashcards were passing transformed series data into the download menu. For combo visualizer cards, that data can omit json_query.parameters, causing downloads to send parameters=[]. This change uses the stored primary card dataset from dashcardData when available, falling back to the previous series result otherwise.

How to verify

1. Create a dashboard with a multi-source visualizer line chart.

• For the example I used, I created a question against Analytics Events → Count by Timestamp, and the second question was just the same but with a filter (Active Subscripion=true)

2. Add a dashboard date filter mapped to the source cards. 3. Apply the date filter. 4. Download the visualizer dashcard results as `.xlsx`. 5. Confirm the XLSX data respects the applied dashboard filter.

Demo

https://www.loom.com/share/96bb25e1b6544cf291a09afade20653a

Checklist

• Tests have been added/updated to cover changes in this PR
• If adding new Loki tests: they pass stress testing

[github-actions]

@andsalves Manual conflict resolution is required on #75743

[github-actions]

@andsalves Manual conflict resolution is required on #75747