Spotnet import, header backfill, staging and counter grouping, faster search

Spotnet (CONCEPT D29):
- Index free.pt fully and import spots with their descriptions, categories
  and NZBs; a spot renames its release, since Spotnet names are more
  trustworthy than names derived from subjects.
- Find passwords in spot descriptions too, and tell "needs a password we
  have" from "needs a password we don't have".

Content inspection:
- List the contents of 7z (.7z.001) archives, SFV sets, nicovideo uploads
  and other archive-like files; mark yEncBin .bin containers as encrypted.
- Take real names from yEnc headers for randomly named files, and merge
  uploads that were split across posts.

Storage (D31, D32):
- Store segment lists zstd-compressed behind the FileStore accessor.
- group:backfill indexes older headers at low priority and pauses when
  the NVMe or HDD part of the database gets too large.

Grouping (D35, D36):
- Lone header segments wait in staged_segments until a second segment of
  their file arrives, which drops the per-article junk binaries.
- Counter grouping joins random-subject uploads by poster, [i/M] counter,
  part count and day.

Search and maintenance (D33, D34):
- A trigram-indexed search_text column, smaller indexes, estimated stats.
- Passes that clean up nonsense names; weekly index maintenance; GC budgets
  per kind.
- Web UI: grey out stale results while a search runs and cancel superseded
  requests. Count only up to 1,000 matches for the page, which made filter
  clicks take seconds (Newznab keeps the 10,000 cap).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/controllers/releases_controller.ts

@@ -18,6 +18,8 @@ export default class ReleasesController {
       sort: qs.sort as SortOrder | undefined,
       page: Number(qs.page) || 1,
       perPage: Number(qs.per_page) || 50,
+      // The page shows "1,000+"; counting further made filter clicks take seconds.
+      countLimit: 1000,
     })
   }
 
@@ -37,6 +39,16 @@ export default class ReleasesController {
     return response.send(nzb.xml)
   }
 
+  /** GET /api/v1/releases/:id/image: the image of the release's spot, read from Usenet. */
+  async image({ params, response }: HttpContext) {
+    const image = await SearchService.spotImage(Number(params.id))
+    if (!image) return response.notFound({ error: 'No image' })
+    response.header('Content-Type', image.type)
+    // A spot's image never changes.
+    response.header('Cache-Control', 'public, max-age=604800, immutable')
+    return response.send(image.data)
+  }
+
   /** GET /api/v1/stats */
   async stats() {
     return SearchService.stats()