feat(api): scene hide + merge-duplicate endpoints for long-press actions

POST /scenes/{id}/hide — marks all playback_sources dead so the scene drops out
of has_playback lists (reversible via dead_at; row kept for dedup/refs).
POST /scenes/{keep_id}/merge/{drop_id} — merges drop into keep via scene_merge
(moves refs/performers/tags/fingerprints/playback). Backs the new tile long-press
menu (hide / mark-duplicate) replacing the dead animated-preview gesture.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/api/scenes.py

@@ -831,6 +831,67 @@ def remove_performer_from_scene(
     session.commit()
 
 
+class SceneHideOut(BaseModel):
+    scene_id: uuid.UUID
+    playback_marked_dead: int
+
+
+@router.post("/{scene_id}/hide", response_model=SceneHideOut)
+def hide_scene(
+    scene_id: uuid.UUID,
+    session: Annotated[Session, Depends(get_session)],
+) -> SceneHideOut:
+    """Ukryj scenę (user long-press → „usuń"). Oznacza wszystkie playback_sources
+    jako dead → scena wypada z list (has_playback=false). Odwracalne w DB (dead_at).
+    Nie kasujemy wiersza sceny — zachowujemy refs/dedup, tylko znika z UI."""
+    from datetime import UTC, datetime
+
+    from app.models.playback_source import PlaybackSource
+
+    if session.get(Scene, scene_id) is None:
+        raise HTTPException(status_code=404, detail="scene not found")
+    rows = session.execute(
+        select(PlaybackSource).where(
+            PlaybackSource.scene_id == scene_id,
+            PlaybackSource.dead_at.is_(None),
+        )
+    ).scalars().all()
+    now = datetime.now(UTC)
+    for p in rows:
+        p.dead_at = now
+        p.dead_reason = "user hid scene (long-press)"
+    session.commit()
+    return SceneHideOut(scene_id=scene_id, playback_marked_dead=len(rows))
+
+
+class SceneMergeOut(BaseModel):
+    keep_id: uuid.UUID
+    dropped_id: uuid.UUID
+
+
+@router.post("/{keep_id}/merge/{drop_id}", response_model=SceneMergeOut)
+def merge_duplicate_scene(
+    keep_id: uuid.UUID,
+    drop_id: uuid.UUID,
+    session: Annotated[Session, Depends(get_session)],
+) -> SceneMergeOut:
+    """Scal `drop_id` w `keep_id` (user long-press → „oznacz duplikat" → wybór drugiej
+    sceny). Przenosi refs/performers/tags/fingerprints/playback (scene_merge), kasuje
+    `drop`. keep = scena na której user trzyma (zostaje), drop = wskazany duplikat."""
+    from app.resolve.scene_merge import MergeError, merge_scenes
+
+    if keep_id == drop_id:
+        raise HTTPException(status_code=400, detail="keep_id == drop_id")
+    if session.get(Scene, keep_id) is None or session.get(Scene, drop_id) is None:
+        raise HTTPException(status_code=404, detail="scene not found")
+    try:
+        merge_scenes(session, keep_id=keep_id, drop_id=drop_id, resolved_by="user_long_press_duplicate")
+    except MergeError as e:
+        raise HTTPException(status_code=400, detail=str(e)) from e
+    session.commit()
+    return SceneMergeOut(keep_id=keep_id, dropped_id=drop_id)
+
+
 class EnrichTagsOut(BaseModel):
     scene_id: uuid.UUID
     added: int