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/source_service.py

@@ -70,6 +70,10 @@ class SourceRecord:
     # plan #697: a running deep-walk that bypasses the Patreon seen-ledger
     # (recovery) vs. a normal backfill. Lets the badge label it "Recovering".
     backfill_bypass_seen: bool
+    # #830: a running deep-walk in RECAPTURE mode (re-grab post bodies/links +
+    # localize on-disk inline images, no media re-download). Lets the badge label
+    # it "Recapturing".
+    backfill_recapture: bool
     # plan #704: cumulative posts processed across the walk's chunks — live
     # progress for the badge.
     backfill_posts: int
@@ -94,6 +98,7 @@ class SourceRecord:
             "backfill_state": self.backfill_state,
             "backfill_chunks": self.backfill_chunks,
             "backfill_bypass_seen": self.backfill_bypass_seen,
+            "backfill_recapture": self.backfill_recapture,
             "backfill_posts": self.backfill_posts,
         }
 
@@ -171,6 +176,7 @@ class SourceService:
             backfill_state=co.get("_backfill_state"),
             backfill_chunks=int(co.get("_backfill_chunks", 0)),
             backfill_bypass_seen=bool(co.get("_backfill_bypass_seen")),
+            backfill_recapture=bool(co.get("_backfill_recapture")),
             backfill_posts=int(co.get("_backfill_posts", 0)),
         )
 
@@ -359,6 +365,34 @@ class SourceService:
         await self.session.commit()
         return await self._row_to_record(source)
 
+    async def start_recapture(self, source_id: int) -> SourceRecord:
+        """#830: arm a RECAPTURE walk — a backfill that re-grabs EVERY post's body
+        + external links (detail-fetching empty bodies) and localizes already-on-
+        disk inline images, WITHOUT re-downloading media. Reuses the entire #693
+        backfill state machine plus a `_backfill_recapture` flag that flips
+        download mode to recapture. Distinct from recovery (which re-downloads the
+        whole source); the two flags are mutually exclusive, so arming recapture
+        clears bypass_seen. Clears prior cursor/chunk/stall state so it walks
+        fresh from the top. The flag is cleared on completion (download_service)
+        and on stop. Recapture is Patreon-only (the native ingester's post-record
+        capture); inert elsewhere. The UI gates the action to Patreon sources."""
+        source = (await self.session.execute(
+            select(Source).where(Source.id == source_id)
+        )).scalar_one_or_none()
+        if source is None:
+            raise LookupError(f"source id={source_id} not found")
+        co = dict(source.config_overrides or {})
+        co["_backfill_state"] = "running"
+        co["_backfill_recapture"] = True
+        co.pop("_backfill_bypass_seen", None)  # mutually exclusive with recovery
+        for k in ("_backfill_cursor", "_backfill_cursor_stalls", "_backfill_chunks",
+                  "_backfill_posts"):
+            co.pop(k, None)
+        source.config_overrides = co
+        source.backfill_runs_remaining = BACKFILL_MAX_CHUNKS
+        await self.session.commit()
+        return await self._row_to_record(source)
+
     async def stop_backfill(self, source_id: int) -> SourceRecord:
         """Plan #693: cancel an in-progress backfill — back to idle/tick mode.
         Clears the running state + cursor/chunk/stall bookkeeping."""
@@ -369,7 +403,8 @@ class SourceService:
             raise LookupError(f"source id={source_id} not found")
         co = dict(source.config_overrides or {})
         for k in ("_backfill_state", "_backfill_cursor", "_backfill_cursor_stalls",
-                  "_backfill_chunks", "_backfill_bypass_seen", "_backfill_posts"):
+                  "_backfill_chunks", "_backfill_bypass_seen", "_backfill_recapture",
+                  "_backfill_posts"):
             co.pop(k, None)
         source.config_overrides = co
         source.backfill_runs_remaining = 0