feat: add 24h cache freshness with auto-refresh on search

- part_scraper_service.ts: new CACHE_TTL_HOURS (24), isCategoryStale()
  checks the most recent scrapedAt for a given ComponentType's mapped
  category, ensureFreshCategory() re-scrapes it synchronously if missing
  or stale (errors are logged, not thrown, so search still falls back to
  whatever is already cached)
- ScrapedPartsController#index: when a typeId filter is provided, the
  corresponding category cache is refreshed eagerly if stale before
  querying results. Free-text searches without a typeId skip this to
  avoid re-scraping every mapped category on every keystroke -
  'node ace scrape:parts' still refreshes everything at once on demand
- 4 new tests covering staleness detection (missing cache, <24h, >24h)
  and that unmapped types never trigger a scrape/network call

app/services/part_scraper_service.ts

@@ -7,6 +7,13 @@ import ScrapedPart from '#models/scraped_part'
 const SOURCE = 'pc-builder.io'
 const BASE_URL = 'https://fr.pc-builder.io'
 
+/**
+ * Default freshness window for the scraped_parts cache. A category is
+ * re-scraped automatically the first time it is searched after this delay
+ * has elapsed since its last successful scrape.
+ */
+const CACHE_TTL_HOURS = 24
+
 /**
  * Maps our own ComponentType names to the corresponding pc-builder.io
  * category slug. Categories not listed here are not scraped.
@@ -139,4 +146,44 @@ async function scrapeAllCategories(): Promise<Record<string, number>> {
   return summary
 }
 
-export { scrapeAllCategories, scrapeComponentType, CATEGORY_SLUGS }
+/**
+ * Returns true if the given ComponentType's category has never been
+ * scraped, or was last scraped more than CACHE_TTL_HOURS ago.
+ */
+async function isCategoryStale(componentType: ComponentType): Promise<boolean> {
+  const mostRecent = await ScrapedPart.query()
+    .where('source', SOURCE)
+    .andWhere('typeId', componentType.id)
+    .orderBy('scrapedAt', 'desc')
+    .first()
+
+  if (!mostRecent) return true
+  return mostRecent.scrapedAt < DateTime.now().minus({ hours: CACHE_TTL_HOURS })
+}
+
+/**
+ * Ensures the cache for a given ComponentType's mapped category is fresh
+ * (scraped within the last CACHE_TTL_HOURS), re-scraping it synchronously
+ * if it's missing or stale. No-op for unmapped types. Scraping errors are
+ * logged but not thrown, so a search still falls back to whatever is
+ * already cached.
+ */
+async function ensureFreshCategory(componentType: ComponentType): Promise<void> {
+  if (!CATEGORY_SLUGS[componentType.name]) return
+  if (!(await isCategoryStale(componentType))) return
+
+  try {
+    await scrapeComponentType(componentType)
+  } catch (error) {
+    logger.error({ type: componentType.name, err: error }, 'Failed to refresh stale category cache')
+  }
+}
+
+export {
+  scrapeAllCategories,
+  scrapeComponentType,
+  ensureFreshCategory,
+  isCategoryStale,
+  CATEGORY_SLUGS,
+  CACHE_TTL_HOURS,
+}