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>

backend/app/services/ingest_core.py

@@ -105,18 +105,28 @@ class Ingester:
     ) -> DownloadResult:
         """Walk + download for one source, returning a gallery-dl-shaped result.
 
-        `mode` is "tick" | "backfill" | "recovery". Recovery bypasses the tier-1
-        seen-ledger AND the dead-letter ledger (tier-2 disk still skips kept
-        files). The walk stops on:
+        `mode` is "tick" | "backfill" | "recovery" | "recapture". Recovery
+        bypasses the tier-1 seen-ledger AND the dead-letter ledger (tier-2 disk
+        still skips kept files). Recapture (#830) is the cheap "re-grab post
+        text" walk: it bypasses the post-record gate (so EVERY post's body +
+        external links are re-captured / detail-fetched) but KEEPS the media
+        seen-ledger — on-disk media is NOT re-downloaded, only surfaced so its
+        ImageRecord's source_filehash can be backfilled for inline-image
+        localization. The walk stops on:
           - budget exhaustion (time_budget_seconds)         → TIMEOUT / PARTIAL
           - tick early-out (seen_threshold contiguous seen)  → success
           - reaching the bottom of the feed                  → success (rc 0)
         A client-level failure (drift / auth / network) fails the whole run loud.
         """
         bypass_seen = mode == "recovery"
+        recapture = mode == "recapture"
+        # Both recovery and recapture re-capture EVERY post's body + links — they
+        # bypass the post-record seen-gate (recovery via bypass_seen, recapture
+        # explicitly). A plain backfill stays gated (capture once per post).
+        recapture_records = bypass_seen or recapture
         # Only deep walks checkpoint their cursor mid-flight (plan #705 #6); a
         # tick has no resumable backfill state.
-        checkpoint = mode in ("backfill", "recovery")
+        checkpoint = mode in ("backfill", "recovery", "recapture")
         ledger_key = self._ledger_key
         # Optional seams (Patreon native ingester): capture pure-text posts that
         # have NO downloadable media so the artist archive is complete. Absent on
@@ -129,6 +139,10 @@ class Ingester:
         written: list[str] = []
         post_records: list[str] = []
         quarantined_paths: list[str] = []
+        # #830 recapture: (on-disk path, CDN source_url) pairs for already-present
+        # media, so phase 3 can backfill the ImageRecord's source_filehash WITHOUT
+        # re-downloading or unlinking the file. Empty outside recapture mode.
+        relink: list[tuple[str, str]] = []
         downloaded = 0
         errors = 0
         quarantined = 0
@@ -165,6 +179,7 @@ class Ingester:
                 quarantined_paths=list(quarantined_paths),
                 written_paths=written,
                 post_record_paths=list(post_records),
+                relink_source_paths=list(relink),
                 stdout="\n".join(log_lines),
                 stderr="",
                 return_code=return_code,
@@ -241,7 +256,7 @@ class Ingester:
                     if rk is not None:
                         pkey, ppid = rk
                         already = (
-                            set() if bypass_seen
+                            set() if recapture_records
                             else self._seen_keys(source_id, [pkey])
                         )
                         if pkey not in already:
@@ -275,6 +290,7 @@ class Ingester:
                 outcomes = self.downloader.download_post(
                     post, media, artist_slug, is_seen=_is_skip,
                     should_stop=lambda: time.monotonic() - start >= time_budget_seconds,
+                    recapture=recapture,
                 )
 
                 to_mark: list[tuple[str, str]] = []
@@ -300,6 +316,12 @@ class Ingester:
                         to_clear.append(key)
                         skipped_count += 1
                         consecutive_seen += 1
+                        # #830 recapture: surface (on-disk path, CDN url) so phase
+                        # 3 can backfill source_filehash for inline-image
+                        # localization — a SEPARATE non-deleting channel, never the
+                        # import list (which would unlink the file, per above).
+                        if recapture and outcome.path is not None:
+                            relink.append((str(outcome.path), media_item.url))
                     elif outcome.status == "skipped_seen":
                         skipped_count += 1
                         consecutive_seen += 1