feat(ingest): Recapture mode — re-grab post bodies/links + localize on-disk inline images (#830)

A plain backfill gates post-body capture on the seen-ledger, so a post whose
media is already on disk AND whose post key is already seen never gets its body
recaptured (operator-flagged: Industrial Lust description missing). Recovery
recaptures unconditionally but re-downloads the whole source.

New 'recapture' walk mode (4th beside tick/backfill/recovery): bypasses the
post-record gate so EVERY post's body + external links are re-captured
(detail-fetching empty bodies) WITHOUT re-downloading on-disk media; and
surfaces already-present media via a separate non-deleting relink channel so the
importer backfills ImageRecord.source_filehash for inline-image localization.

- ingest_core: recapture mode + recapture_records gate bypass + relink collect
- patreon_downloader: recapture surfaces seen-on-disk as skipped_disk(path),
  never refetches seen-missing media, still downloads genuinely-new
- importer.relink_source_filehash: NULL-only sha256 backfill, never unlinks
- download_service: mode derivation + phase-3 relink loop + lifecycle clear
- source_service/api: start_recapture + backfill_recapture field + action
- frontend: Recapture kebab action + 'Recapturing' badge across SourceActions/
  Row/Card/SubscriptionsTab + sources store
- tests across ingester/downloader/importer/source_service/api/download_service

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/stores/sources.js

@@ -131,6 +131,14 @@ export const useSourcesStore = defineStore('sources', () => {
     _patchSource(body)
     return body
   }
+  // #830: arm a recapture walk (Patreon-only) — re-grab every post's body +
+  // external links and localize on-disk inline images, WITHOUT re-downloading
+  // media. Shares the backfill lifecycle/badge; stop via stopBackfill.
+  async function recaptureSource(id, artistIdHint = null) {
+    const body = await api.post(`/api/sources/${id}/backfill`, { body: { action: 'recapture' } })
+    _patchSource(body)
+    return body
+  }
 
   // Plan #708 B4: dry-run preview — count what a backfill WOULD download
   // (native platforms), without downloading. Read-only, so no cache invalidate.
@@ -167,6 +175,7 @@ export const useSourcesStore = defineStore('sources', () => {
     startBackfill,
     stopBackfill,
     recoverSource,
+    recaptureSource,
     previewSource,
     findOrCreateArtist, autocompleteArtist,
     loadScheduleStatus,