Provider and Model Views filters re-query the database on every page load

Problem/Motivation

UsageProviderFilter::getValueOptions() and UsageModelFilter::getValueOptions() run an uncached SELECT DISTINCT against ai_metering_usage on every request. The in-memory guard (if (isset($this->valueOptions))) does not survive between page loads, so every admin user hitting the log view triggers two redundant queries — including a full table scan on model_id, which has no index.

Steps to reproduce

1. Enable query logging (Devel or WebProfiler).
2. Load /admin/reports/ai-metering/log in two separate sessions.
3. Observe SELECT DISTINCT provider_id FROM {ai_metering_usage} running on every load.

Proposed resolution

Cache the options with a Cache::PERMANENT entry tagged ai_metering:usage, invalidated when a new usage record is written:

use Drupal\Core\Cache\Cache;

public function getValueOptions(): void {
  if (isset($this->valueOptions)) {
    return;
  }
  $cid = 'ai_metering:filter_options:providers';
  if ($cached = \Drupal::cache()->get($cid)) {
    $this->valueOptions = $cached->data;
    return;
  }
  // ... existing SELECT DISTINCT query ...
  \Drupal::cache()->set($cid, $this->valueOptions, Cache::PERMANENT, ['ai_metering:usage']);
}

Inject CacheBackendInterface for testability rather than using the static call.

Remaining tasks

• Apply the pattern to both UsageProviderFilter and UsageModelFilter
• Add Cache::invalidateTags(['ai_metering:usage']) in the usage record writer
• Extend ViewsFilterTest to assert cache hit on second call

UI / API / Data model changes

Internal change only. No visible impact on the filter dropdowns.

AI assistance

Cache strategy and proposed code drafted with AI assistance and reviewed by the module maintainer.