feat(patreon): recovery UI + gallery-dl cutover — build step 5 (plan #697)

Final step of the native Patreon ingester: a first-class Recovery action,
and removal of the now-dead gallery-dl Patreon path.

Recovery (rules #23/#24/#27 — full product, with UI):
- source_service.start_recovery arms the #693 backfill state machine PLUS
  `_backfill_bypass_seen`, flipping download mode to recovery (bypass the
  seen-ledger to re-fetch dropped-and-deleted near-dups and re-evaluate
  under the current pHash threshold). Stop via the shared stop_backfill.
- SourceRecord exposes backfill_bypass_seen; POST /sources/{id}/backfill
  gains action="recover".
- Frontend: Recovery button (Patreon-only, mdi-backup-restore) on SourceRow
  + SourceCard; the running badge labels "Recovering (N)" vs "Backfilling
  (N)"; the Stop tooltip says "Stop recovery". sources.js recoverSource +
  SubscriptionsTab onRecover.

Cutover (rule #22 — no legacy):
- gallery_dl: removed PLATFORM_DEFAULTS["patreon"], the patreon
  files/cursor branch in _build_config_for_source, and the patreon/Mux
  yt-dlp Referer/Origin block (was patreon-specific and wrongly tagged the
  other platforms' yt-dlp fetches; native ingester owns it now).
- download_service: removed the dead campaign-id-retry helpers
  (_looks_like_campaign_id_failure / _CAMPAIGN_ID_FAILURE_PATTERN) and
  _effective_url. Vanity→campaign resolution + resume_cursor + the
  cursor/PARTIAL lifecycle stay — they serve the native ingester.

Tests: removed the two obsolete patreon-gallery-dl config tests (yt-dlp
Referer, resume-cursor); repointed the generic skip-value config tests to
subscribestar; added start_recovery + recover-endpoint coverage
(backfill_bypass_seen). gallery-dl stays for the other 5 platforms.

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

tests/test_gallery_dl_service.py

@@ -260,7 +260,7 @@ def test_build_config_emits_tick_skip_value(gdl):
     scans once 20 contiguous archived items are seen."""
     from backend.app.services.gallery_dl import TICK_SKIP_VALUE
     cfg = gdl._build_config_for_source(
-        platform="patreon",
+        platform="subscribestar",
         source_config=SourceConfig(),
         artist_slug="alice",
         skip_value=TICK_SKIP_VALUE,
@@ -273,7 +273,7 @@ def test_build_config_emits_backfill_skip_value(gdl):
     full post history."""
     from backend.app.services.gallery_dl import BACKFILL_SKIP_VALUE
     cfg = gdl._build_config_for_source(
-        platform="patreon",
+        platform="subscribestar",
         source_config=SourceConfig(),
         artist_slug="alice",
         skip_value=BACKFILL_SKIP_VALUE,
@@ -318,23 +318,17 @@ def test_categorize_tier_limited_wins_over_partial(gdl):
     assert etype == ErrorType.TIER_LIMITED
 
 
-def test_default_config_forwards_patreon_referer_to_ytdl(gdl):
-    """Operator-flagged 2026-06-01: Mux video playback restrictions reject
-    yt-dlp's manifest fetch when Referer/Origin don't match Patreon. The
-    fix is a static `downloader.ytdl.raw-options.http_headers` block, so
-    it's enough to assert the keys land in the default config."""
-    cfg = gdl._get_default_config()
-    headers = cfg["downloader"]["ytdl"]["raw-options"]["http_headers"]
-    assert headers["Referer"] == "https://www.patreon.com/"
-    assert headers["Origin"] == "https://www.patreon.com"
-
-
-# --- Cursor-paged backfill (plan #689) -------------------------------------
+# --- 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():
-    # gallery-dl logs `Cursor: <token>` per page (debug → stderr); the last
-    # is the furthest-progressed resume point.
+    # 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"
@@ -347,18 +341,3 @@ 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
-
-
-def test_build_config_patreon_resume_cursor_overrides_default(gdl):
-    # No resume cursor → PLATFORM_DEFAULTS leaves the log-only `cursor: True`.
-    fresh = gdl._build_config_for_source(
-        "patreon", SourceConfig(), "alice", skip_value=True,
-    )
-    assert fresh["extractor"]["patreon"]["cursor"] is True
-
-    # Resume cursor set → gallery-dl restarts the walk from that page.
-    resumed = gdl._build_config_for_source(
-        "patreon", SourceConfig(resume_cursor="03:CCCC:ddd"), "alice",
-        skip_value=True,
-    )
-    assert resumed["extractor"]["patreon"]["cursor"] == "03:CCCC:ddd"