fix: a post record is marked seen only after it is upserted, and an hourly sweep dates the posts killed walks left undated (#4436)

ingest_core marked a post's record key seen when it wrote _post.json, but
the record reaches the database (and dates the post and its images) only
in phase 3. A walk killed before phase 3 left posts the ledger called
recorded and the database never dated; ticks early-out long before
reaching them again. Keys now join the media in mark_seen_after_import.

date_posts_from_records finds each undated native post's record under
its artist's folder and upserts it with the post's own source. Hourly on
maintenance_long; an empty query once everything is dated.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LVjrnpQjRgHdvq95rASoiR

backend/app/services/ingest_core.py

@@ -289,6 +289,11 @@ class Ingester:
         # Media handed to phase 3 for import. Marked seen by phase 3 once the
         # import has run (`mark_seen_after_import`), not here — see there.
         fetched: list[tuple[str, str]] = []
+        # Post-record keys written this walk. Marked with the media, after
+        # phase 3 has upserted the records — marking them at write time left a
+        # walk killed before phase 3 with posts the ledger calls recorded that
+        # the database never dated, and no later tick walks back to them (#4436).
+        recorded: list[tuple[str, str]] = []
         downloaded = 0
         errors = 0
         quarantined = 0
@@ -342,7 +347,9 @@ class Ingester:
                 written_paths=written,
                 post_record_paths=list(post_records),
                 relink_source_paths=list(relink),
-                mark_seen_after_import=lambda: self._mark_seen(source_id, fetched),
+                mark_seen_after_import=lambda: self._mark_seen(
+                    source_id, fetched + recorded,
+                ),
                 stdout="\n".join(log_lines),
                 stderr="",
                 return_code=return_code,
@@ -511,7 +518,7 @@ class Ingester:
                                     posts_with_body += 1
                             if rec.path is not None:
                                 post_records.append(str(rec.path))
-                                self._mark_seen(source_id, [(pkey, ppid)])
+                                recorded.append((pkey, ppid))
                             # Per-post handling line in the run stdout (the existing
                             # "Raw stdout" panel) — the downloader already read the
                             # post; we only format its outcome here. post_type beside