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- Web UI: grey out stale results while a search runs and cancel superseded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>

commands/workers/Collection.ts

@@ -49,6 +49,10 @@ export default class CollectionWorker extends BaseCommand {
         if (content?.named) this.logger.info(`"${file.filename}" got its real name from par2.`)
         if (content?.contentType === 'nzbe') this.logger.info(`"${file.filename}" is an encrypted NZB container.`)
         if (content?.contentType === 'rclone') this.logger.info(`"${file.filename}" is rclone-encrypted.`)
+        if (content?.yencName) this.logger.info(`"${file.filename}" is "${content.yencName}" (yEnc name).`)
+        if (content?.nicovideo) this.logger.info(`"${file.filename}" → "${content.nicovideo}".`)
+        if (content?.sfvMoved) this.logger.info(`SFV "${file.filename}" moved ${content.sfvMoved} files into its release.`)
+        if (content?.contentType === 'yencbin') this.logger.info(`"${file.filename}" is a yEncBin encrypted container.`)
         if (content?.nzb) {
           const n = content.nzb
           this.logger.info(`NZB "${file.filename}": ${n.listed} files (${n.known} known, ${n.added} added) → "${n.releaseName}".`)