fix(subscriptions): hide sidecar synthetic Sources + prefer real on lookup

Two coupled bugs surfaced 2026-05-31 by the Subscriptions UI showing
"phantom" subscriptions like `sidecar:patreon:dpmaker`:

1. `SourceService.list()` returned every Source, no filter on URL.
   alembic 0022 (2026-05-26) consolidated old per-post-URL Sources into
   one canonical row per (artist, platform); when no real campaign URL
   was salvageable it rewrote the canonical to `sidecar:<plat>:<slug>`
   enabled=false as a disabled anchor. The UI then listed those
   anchors as if they were polls — disabled, but visible. Fix: `list()`
   excludes `url LIKE 'sidecar:%'` by default; `include_synthetic=True`
   opts back in for admin tooling.

2. `importer._source_for_sidecar` picked the lowest-id Source for
   (artist, platform). When alembic 0022 had rewritten a per-post row
   into a synthetic anchor (lower id) AND the operator later added the
   real subscription (higher id), every gallery-dl download silently
   attached its Post to the SYNTHETIC instead of the real Source. Fix:
   prefer a non-`sidecar:%` URL when one exists; fall back to the
   synthetic; only create a new synthetic when nothing exists for
   (artist, platform).

alembic 0028 is the data half: for every (artist, platform) with both
a synthetic AND a real Source, pre-merge Post+ImageProvenance
collisions on the canonical, bulk-repoint Posts/ImageProvenance/
DownloadEvent.source_id onto the real Source, and delete the
synthetic. Lone synthetics (no real twin) are left intact — they
anchor real imported content the operator may still want; the
list-filter hides them so they no longer surface as phantoms.

backend/app/services/importer.py

@@ -261,24 +261,44 @@ class Importer:
     def _source_for_sidecar(
         self, *, artist_id: int, platform: str, artist_slug: str,
     ) -> Source:
-        """Filesystem-import sidecar Source resolver.
+        """Sidecar-import Source resolver. Used by both filesystem imports
+        and gallery-dl downloads (both write sidecar JSON, both flow through
+        _apply_sidecar / _capture_attachment).
 
         Source represents a subscription feed (one per artist+platform — the
-        gallery-dl URL polled by the FC-3 downloader). The filesystem importer
-        used to call _find_or_create_source(url=sd.post_url), which created
-        one Source row per post URL — 100s of junk Sources per artist, all
-        with enabled=True, polluting the artist detail page and tricking the
+        URL polled by the FC-3 downloader). The filesystem importer used to
+        call _find_or_create_source(url=sd.post_url), creating one Source
+        row per post URL — 100s of junk Sources per artist, all with
+        enabled=True, polluting the artist detail page and tricking the
         subscription checker into trying to poll patreon post URLs as feeds.
-        Operator-flagged 2026-05-26.
+        Operator-flagged 2026-05-26; consolidated via alembic 0022.
 
-        New behaviour: if any Source row exists for (artist_id, platform),
-        reuse it regardless of its URL — the artist's real subscription Source
-        (created by the downloader / extension / UI) is the canonical
-        attachment point for filesystem-imported posts. If none exists, create
-        ONE synthetic anchor with url='sidecar:<platform>:<artist_slug>' and
-        enabled=False (so the subscription checker doesn't poll it).
+        Resolution order: prefer a real (non-sidecar) Source over a
+        synthetic anchor. When alembic 0022 ran, it may have rewritten
+        per-post Sources into `sidecar:<platform>:<slug>` synthetic
+        anchors. If the operator later added the real subscription, both
+        rows now coexist. A naive `ORDER BY id ASC LIMIT 1` lookup would
+        pick the older synthetic and silently attach every gallery-dl
+        download to the wrong Source — operator-flagged 2026-05-31 after
+        the Subscriptions UI surfaced the phantom anchors. Pick the real
+        one when one exists; fall back to the synthetic; only create a
+        new synthetic when nothing exists for (artist, platform).
         """
-        stmt = (
+        real_stmt = (
+            select(Source)
+            .where(
+                Source.artist_id == artist_id,
+                Source.platform == platform,
+                ~Source.url.like("sidecar:%"),
+            )
+            .order_by(Source.id.asc())
+            .limit(1)
+        )
+        real = self.session.execute(real_stmt).scalar_one_or_none()
+        if real is not None:
+            return real
+
+        any_stmt = (
             select(Source)
             .where(
                 Source.artist_id == artist_id,
@@ -288,7 +308,7 @@ class Importer:
             .limit(1)
         )
         return self._get_or_create(
-            stmt,
+            any_stmt,
             lambda: Source(
                 artist_id=artist_id,
                 platform=platform,

backend/app/services/source_service.py

@@ -151,10 +151,18 @@ class SourceService:
 
     async def list(
         self, artist_id: int | None = None, failing: bool = False,
+        include_synthetic: bool = False,
     ) -> list[SourceRecord]:
         stmt = select(Source, Artist).join(Artist, Artist.id == Source.artist_id)
         if artist_id is not None:
             stmt = stmt.where(Source.artist_id == artist_id)
+        if not include_synthetic:
+            # Filesystem-import sidecar anchors (importer._source_for_sidecar)
+            # have url='sidecar:<platform>:<slug>' and exist only to give
+            # imported Posts a NOT-NULL Source FK. They aren't pollable
+            # feeds; the Subscriptions UI used to render them as phantom
+            # subscriptions. Hide by default.
+            stmt = stmt.where(~Source.url.like("sidecar:%"))
         if failing:
             # Worst-first so the rollup card surfaces the loudest failures.
             stmt = stmt.where(Source.consecutive_failures > 0).order_by(