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>

tests/test_download_service.py

@@ -60,8 +60,10 @@ def _make_fake_dl_result(
     *, success=True, written_paths=None, quarantined_paths=None,
     files_downloaded=0, error_type=None, error_message=None,
     stdout="", stderr="", cursor=None, run_stats=None, posts_processed=0,
+    relink_source_paths=None,
 ):
     return SimpleNamespace(
+        relink_source_paths=relink_source_paths or [],
         success=success,
         url="https://patreon.com/alice",
         artist_slug="alice",
@@ -793,6 +795,31 @@ async def test_recovery_mode_selected_and_flag_cleared_on_complete(
     assert "_backfill_bypass_seen" not in co
 
 
+@pytest.mark.asyncio
+async def test_recapture_mode_selected_and_flag_cleared_on_complete(
+    db, db_sync, tmp_path, seed_artist_and_source,
+):
+    """#830: `_backfill_recapture` alongside a running backfill selects recapture
+    mode. A clean rc=0 walk completes the shared lifecycle AND clears the
+    recapture flag so the next tick is a plain tick again."""
+    _artist, source = seed_artist_and_source
+    source.config_overrides = {"_backfill_state": "running", "_backfill_recapture": True}
+    source.backfill_runs_remaining = 5
+    await db.commit()
+
+    svc, calls = _backfill_svc(db, db_sync, tmp_path, _make_fake_dl_result(
+        success=True, written_paths=[], files_downloaded=0,
+    ))
+    await svc.download_source(source.id)
+
+    assert calls[0]["mode"] == "recapture"
+    co = (await db.execute(
+        select(Source.config_overrides).where(Source.id == source.id)
+    )).scalar_one()
+    assert co.get("_backfill_state") == "complete"
+    assert "_backfill_recapture" not in co
+
+
 @pytest.mark.asyncio
 async def test_partial_error_type_maps_to_ok_status(
     db, db_sync, tmp_path, seed_artist_and_source,