Fix explore paging for non-date sorts (#24392)

* fix explore paging for non-date sorts

Explore paged every sort by passing the last row's `start_time` as a `before` or `after` cursor, which only works when rows are ordered by `start_time`. For score, speed, and relevance sorts, each page dropped every match newer than that row and repeated older rows from earlier pages, so infinite scroll stopped after a few pages. `/events` and `/events/search` now accept `offset`, and Explore pages non-date sorts by offset. Date sorts keep the cursor because `useSWRInfinite` only revalidates the first page, and cursor keys for later pages follow it while offset keys don't. Score and speed sorts on `/events` break ties on `id` so offset pages stay stable.

* order search ties by id and reject negative offsets

`/events/search` sorted in Python over a query with no `ORDER BY`, so tied scores, speeds, or distances kept whatever order SQLite returned, which isn't guaranteed to match across page requests. The query is now ordered by id and the stable sorts keep that order for ties. `offset` also accepted negative values, which sliced from the end of the search results.

frigate/test/http_api/test_http_event.py

@@ -168,6 +168,29 @@ class TestHttpApp(BaseTestHttp):
             assert events[0]["id"] == id
             assert events[1]["id"] == id2
 
+    def test_get_event_list_offset_pages_score_sort(self):
+        now = datetime.now().timestamp()
+        scores = [0.6, 0.9, 0.7, 0.95, 0.8]
+
+        with AuthTestClient(self.app) as client:
+            for i, score in enumerate(scores):
+                super().insert_mock_event(
+                    f"event-{i}", start_time=now + i, data={"score": score}
+                )
+
+            params = {"sort": "score_desc"}
+            full = [e["id"] for e in client.get("/events", params=params).json()]
+            paged = [
+                e["id"]
+                for offset in (0, 2, 4)
+                for e in client.get(
+                    "/events", params={**params, "limit": 2, "offset": offset}
+                ).json()
+            ]
+
+            assert full == ["event-3", "event-1", "event-4", "event-2", "event-0"]
+            assert paged == full
+
     def test_get_event_list_match_multilingual_attribute(self):
         event_id = "123456.zh"
         attribute = "中文标签"
@@ -219,6 +242,85 @@ class TestHttpApp(BaseTestHttp):
             assert len(events) == 1
             assert events[0]["id"] == event_id
 
+    def test_events_search_offset_pages_score_sort(self):
+        now = datetime.now().timestamp()
+        scores = [0.6, 0.9, 0.7, 0.95, 0.8]
+        ids = [f"event-{i}" for i in range(len(scores))]
+        mock_embeddings = Mock()
+        mock_embeddings.search_thumbnail.return_value = [
+            (event_id, 0.1 * i) for i, event_id in enumerate(ids)
+        ]
+
+        self.app.frigate_config.semantic_search.enabled = True
+        self.app.embeddings = mock_embeddings
+
+        with AuthTestClient(self.app) as client:
+            for i, score in enumerate(scores):
+                super().insert_mock_event(
+                    ids[i], start_time=now + i, data={"score": score}
+                )
+
+            params = {
+                "search_type": "similarity",
+                "event_id": ids[0],
+                "sort": "score_desc",
+            }
+            paged = [
+                e["id"]
+                for offset in (0, 2, 4)
+                for e in client.get(
+                    "/events/search",
+                    params={**params, "limit": 2, "offset": offset},
+                ).json()
+            ]
+
+            assert paged == ["event-3", "event-1", "event-4", "event-2", "event-0"]
+
+    def test_events_search_offset_pages_orders_ties_by_id(self):
+        now = datetime.now().timestamp()
+        ids = ["event-c", "event-a", "event-b"]
+        mock_embeddings = Mock()
+        mock_embeddings.search_thumbnail.return_value = [
+            (event_id, 0.1) for event_id in ids
+        ]
+
+        self.app.frigate_config.semantic_search.enabled = True
+        self.app.embeddings = mock_embeddings
+
+        with AuthTestClient(self.app) as client:
+            for i, event_id in enumerate(ids):
+                super().insert_mock_event(
+                    event_id, start_time=now + i, data={"score": 0.8}
+                )
+
+            for sort in ("score_desc", "relevance"):
+                params = {
+                    "search_type": "similarity",
+                    "event_id": ids[0],
+                    "sort": sort,
+                }
+                paged = [
+                    e["id"]
+                    for offset in (0, 1, 2)
+                    for e in client.get(
+                        "/events/search",
+                        params={**params, "limit": 1, "offset": offset},
+                    ).json()
+                ]
+
+                assert paged == ["event-a", "event-b", "event-c"]
+
+    def test_event_list_rejects_negative_offset(self):
+        with AuthTestClient(self.app) as client:
+            response = client.get("/events", params={"offset": -5})
+            assert response.status_code == 422
+
+            response = client.get(
+                "/events/search",
+                params={"query": "car", "offset": -5},
+            )
+            assert response.status_code == 422
+
     def test_similarity_search_hides_unauthorized_anchor_event(self):
         mock_embeddings = Mock()
         self.app.frigate_config.semantic_search.enabled = True