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/api/sources.py

@@ -138,14 +138,16 @@ async def delete_source(source_id: int):
 
 @sources_bp.route("/<int:source_id>/backfill", methods=["POST"])
 async def set_backfill(source_id: int):
-    """Plan #693/#697: start/stop a run-until-done backfill, or start a recovery.
-    Body: `{"action": "start" | "stop" | "recover"}` (default "start"). 'start'
-    walks the full post history in time-boxed chunks until it reaches the bottom
-    (then the source shows 'complete'); 'recover' is the same walk but bypasses
-    the Patreon seen-ledger to re-fetch dropped-and-deleted near-dups under the
-    current pHash threshold; 'stop' cancels either back to tick mode. Returns the
-    updated source dict (incl. backfill_state / backfill_chunks /
-    backfill_bypass_seen)."""
+    """Plan #693/#697 + #830: start/stop a backfill, or start a recovery /
+    recapture. Body: `{"action": "start" | "stop" | "recover" | "recapture"}`
+    (default "start"). 'start' walks the full post history in time-boxed chunks
+    until it reaches the bottom (then the source shows 'complete'); 'recover' is
+    the same walk but bypasses the Patreon seen-ledger to re-fetch
+    dropped-and-deleted near-dups under the current pHash threshold; 'recapture'
+    re-grabs EVERY post's body + external links and localizes on-disk inline
+    images WITHOUT re-downloading media; 'stop' cancels any back to tick mode.
+    Returns the updated source dict (incl. backfill_state / backfill_chunks /
+    backfill_bypass_seen / backfill_recapture)."""
     from pathlib import Path
 
     from ..services.credential_service import CredentialService
@@ -157,10 +159,10 @@ async def set_backfill(source_id: int):
 
     payload = await request.get_json(silent=True) or {}
     action = payload.get("action", "start")
-    if action not in ("start", "stop", "recover"):
+    if action not in ("start", "stop", "recover", "recapture"):
         return _bad(
             "invalid_action",
-            detail="action must be 'start', 'stop', or 'recover'",
+            detail="action must be 'start', 'stop', 'recover', or 'recapture'",
         )
 
     # Pre-flight (plan #703 #2): before arming a deep walk on a native-ingester
@@ -170,7 +172,7 @@ async def set_backfill(source_id: int):
     # platforms: gallery-dl verify is a slow --simulate subprocess, too heavy for
     # an arm action. The credential read happens in a session that's CLOSED
     # before the verify network call (don't hold a DB conn across the request).
-    if action in ("start", "recover"):
+    if action in ("start", "recover", "recapture"):
         async with get_session() as session:
             rec = await SourceService(session).get(source_id)
             if rec is None:
@@ -200,6 +202,8 @@ async def set_backfill(source_id: int):
                 record = await svc.start_backfill(source_id)
             elif action == "recover":
                 record = await svc.start_recovery(source_id)
+            elif action == "recapture":
+                record = await svc.start_recapture(source_id)
             else:
                 record = await svc.stop_backfill(source_id)
         except LookupError: