fix(api): collapse same-origin playback sources on scene detail

A merged scene often aggregates several uploads from ONE tube (re-encodes / 4K
dups). bug-report aa79a995 "why 2 links, both porntrex?" = same scene std + 4K
(porntrex 2591377 + 2593449 "...in 4K"). In the UI these are indistinguishable
links to one hoster (same extractor). Keep one best per origin: prefer duration
matching the scene → any duration → first (origin-asc stable). Dead already filtered.

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

app/api/scenes.py

@@ -709,6 +709,27 @@ def _build_scene_out(session: Session, scene: Scene) -> SceneOut:
         .scalars()
         .all()
     )
+    # Collapse źródła dzielące ten sam origin (hoster). Zmergowana scena często agreguje
+    # kilka uploadów z JEDNEGO tube'a (re-enkody / wersje 4K: bug-report aa79a995 "2 linki,
+    # oba do porntrex" = ta sama scena std+4K) — w UI to nierozróżnialne linki do tego
+    # samego hostera (resolvują tym samym extractorem). Zostawiamy jeden najlepszy per
+    # origin: preferuj długość zgodną ze sceną (realny match) → jakąkolwiek długość →
+    # pierwszy (stabilnie, query jest origin-asc). Martwe już odfiltrowane (dead_at).
+    def _origin_pick_key(p: PlaybackSource) -> tuple[int, int]:
+        dur_match = (
+            0 if (scene.duration_sec and p.duration_sec
+                  and abs(p.duration_sec - scene.duration_sec) <= 5) else 1
+        )
+        return (dur_match, 0 if p.duration_sec else 1)
+
+    _best_by_origin: dict[str, PlaybackSource] = {}
+    for p in playback_rows:
+        key = p.origin or ""
+        cur = _best_by_origin.get(key)
+        if cur is None or _origin_pick_key(p) < _origin_pick_key(cur):
+            _best_by_origin[key] = p
+    playback_rows = list(_best_by_origin.values())
+
     playback_out: list[PlaybackSourceOut] = []
     for p in playback_rows:
         out = PlaybackSourceOut.model_validate(p)