CSV export ignores active Views filters on the usage log

Problem/Motivation

The "Export CSV" link on /admin/reports/ai-metering/log calls a
custom controller route that queries ai_metering_usage directly.
It ignores any exposed filters the user has set (Provider, Model, Period).
Filtering to a specific provider then exporting gives the full unfiltered dataset.

The exports on /admin/reports/ai-metering and
/admin/reports/ai-metering/by-role are out of scope — those
pages have no pagination yet and their export behavior is unchanged.

Steps to reproduce

1. Go to /admin/reports/ai-metering/log.
2. Set the Provider filter to anthropic and apply.
3. Click "Export CSV".
4. Observe: the downloaded file contains rows from all providers.

Environment

• ai_metering 1.0.0-alpha1

Proposed resolution

Replace the custom CSV controller with a
views_data_export
display added to the ai_metering_usage_log View. The display
inherits all exposed filters, so the export reflects exactly what the user sees.
Batch processing handles large logs without timeouts.

Remaining tasks

• Add drupal/views_data_export to composer.json.
• Add a VDE CSV display to ai_metering_usage_log.view.yml.
• Remove or redirect the legacy CSV controller route.
• Add a test asserting the export respects the active Provider filter.
• Review.

User interface changes

The "Export CSV" link triggers a views_data_export batch instead of an
immediate download. UX is otherwise unchanged.

API changes

None.

Data model changes

None.

AI assistance

N/A