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>

tests/test_gallery_dl_service.py

@@ -8,7 +8,6 @@ from backend.app.services.gallery_dl import (
     ErrorType,
     GalleryDLService,
     SourceConfig,
-    parse_last_cursor,
 )
 
 
@@ -316,28 +315,6 @@ def test_categorize_tier_limited_wins_over_partial(gdl):
         return_code=1, stdout=stdout, stderr=stderr,
     )
     assert etype == ErrorType.TIER_LIMITED
-
-
-# --- Cursor parsing (plan #689 / native ingester #697) ---------------------
-# parse_last_cursor is retained post-cutover: the native Patreon ingester emits
-# `Cursor: <token>` per page into DownloadResult.stdout and download_service
-# checkpoints the last one. (The gallery-dl Patreon `files`/`cursor` config and
-# the Mux yt-dlp Referer block were removed at the #697 cutover, along with the
-# tests that pinned them.)
-
-
-def test_parse_last_cursor_returns_last_match_across_streams():
-    # One `Cursor: <token>` line per page; the last is the furthest-progressed
-    # resume point.
-    stderr = (
-        "[patreon][debug] Cursor: 03:AAAA:bbb\n"
-        "[urllib3] GET ...\n"
-        "[patreon][debug] Cursor: 03:CCCC:ddd\n"
-    )
-    assert parse_last_cursor("", stderr) == "03:CCCC:ddd"
-
-
-def test_parse_last_cursor_scans_stdout_too_and_none_when_absent():
-    assert parse_last_cursor("Cursor: 99:ZZZ", "") == "99:ZZZ"
-    assert parse_last_cursor("no marker here", "still nothing") is None
-    assert parse_last_cursor("", "") is None
+# (The cursor-parsing tests were removed in plan #704: parse_last_cursor is gone
+# — the native ingester now carries its checkpoint cursor as a structured
+# DownloadResult.cursor field instead of a `Cursor:` log line to scrape.)