feat(patreon): structured ingester results + quarantine surfacing — #704 step 1

The native ingester faked gallery-dl stdout (`Cursor:` lines, summary) and
phase 3 regex-scraped it back — so Patreon run-stats were mostly zero and
quarantine stats blank. We own the ingester, so it now RETURNS structured
data and phase 3 reads it directly.

- DownloadResult gains run_stats/cursor/posts_processed (None/0 on the
  gallery-dl path, which keeps the text route).
- Ingester builds real run_stats from per-media outcome counts, sets the
  checkpoint cursor structurally (no fake `Cursor:` stdout), and counts
  posts processed. download_service phase 3 uses dl_result.run_stats when
  present; the backfill lifecycle + TIMEOUT→PARTIAL block checkpoint
  dl_result.cursor instead of parse_last_cursor(stdout).
- #4 quarantine: PatreonDownloader reports a distinct "quarantined"
  MediaOutcome (with the _quarantine dest); the ingester surfaces a real
  files_quarantined + quarantined_paths + run_stats.quarantined_count
  (was hardcoded 0). Quarantined media isn't written or marked seen.
- Cleanup: parse_last_cursor + _CURSOR_RE (and the now-unused `import re`)
  removed from gallery_dl — the structured cursor replaced the scrape.

Tests: ingester result carries real run_stats/cursor/posts_processed +
quarantine counts; downloader quarantines an invalid file as "quarantined";
backfill cursor tests pass cursor= structurally; dropped the
parse_last_cursor tests.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

backend/app/services/gallery_dl.py

@@ -13,7 +13,6 @@ from __future__ import annotations
 import asyncio
 import json
 import logging
-import re
 import subprocess
 import sys
 import tempfile
@@ -156,6 +155,14 @@ class DownloadResult:
     duration_seconds: float = 0.0
     started_at: str | None = None
     completed_at: str | None = None
+    # Plan #704 — structured fields the NATIVE ingester populates directly (None
+    # on the gallery-dl path, which keeps the regex-over-stdout route). When set,
+    # phase 3 reads these instead of scraping the text it would otherwise have to
+    # reconstruct: `run_stats` mirrors _compute_run_stats' shape; `cursor` is the
+    # backfill checkpoint the ingester knows exactly (no parse_last_cursor).
+    run_stats: dict | None = None
+    cursor: str | None = None
+    posts_processed: int = 0
 
 
 def _summarize_validation_failures(failures: list[dict]) -> str:
@@ -172,20 +179,9 @@ def _summarize_validation_failures(failures: list[dict]) -> str:
     return f"{n} files quarantined ({top_count}× {top_reason}, mixed)"
 
 
-# The native Patreon ingester emits its pagination cursor as `Cursor: <token>`
-# — one line per fetched page — into the DownloadResult stdout (mirroring the
-# convention gallery-dl used before the #697 cutover, so the backfill lifecycle
-# stayed unchanged). The LAST such line is the furthest-progressed page, i.e.
-# the resume point. We scan both streams (be defensive) and take the final
-# match; download_service checkpoints it as the next chunk's resume_cursor.
-# Survives a time-boxed chunk too: the ingester emits the cursor for a page when
-# it STARTS it, so an interrupted walk still yields its last cursor.
-_CURSOR_RE = re.compile(r"Cursor:\s*(\S+)")
-
-
-def parse_last_cursor(stdout: str, stderr: str) -> str | None:
-    matches = _CURSOR_RE.findall(f"{stdout or ''}\n{stderr or ''}")
-    return matches[-1] if matches else None
+# (parse_last_cursor was removed in plan #704: the native ingester now carries
+# its checkpoint cursor as a structured DownloadResult.cursor field, so there is
+# no log text to scrape — and gallery-dl platforms never had a cursor.)
 
 
 class GalleryDLService: