Channel features: subscribers, new-videos badges, activity-driven sync

- Store subscriber count from YouTube statistics and show it on channel page
- Sync 50 videos per channel with playlistItems pagination support
- Show per-channel and per-category new-videos counters (2-day window)
- Replace hourly videos sync with activity trigger (2h idle) and
  incremental backfill (hard cap 200 per channel)
- Clicking the sidebar new-videos count filters the category feed to
  recent videos only (new_only)
- Update agent-team docs: deploy after green checks

tests/test_sync_trigger.py

@@ -0,0 +1,159 @@
+import json
+from datetime import datetime, timedelta, timezone
+from types import SimpleNamespace
+
+from app.services import sync_trigger
+
+
+def _now():
+    return datetime.now(timezone.utc)
+
+
+def test_is_videos_sync_due_without_finished_at():
+    assert sync_trigger.is_videos_sync_due(None, _now(), 2) is True
+
+
+def test_is_videos_sync_due_after_idle():
+    finished = (_now() - timedelta(hours=3)).isoformat()
+    assert sync_trigger.is_videos_sync_due(finished, _now(), 2) is True
+
+
+def test_is_videos_sync_due_at_exact_threshold():
+    finished = (_now() - timedelta(hours=2)).isoformat()
+    assert sync_trigger.is_videos_sync_due(finished, _now(), 2) is True
+
+
+def test_is_videos_sync_due_before_idle():
+    finished = (_now() - timedelta(hours=1)).isoformat()
+    assert sync_trigger.is_videos_sync_due(finished, _now(), 2) is False
+
+
+def test_is_videos_sync_due_unparseable_finished_at():
+    assert sync_trigger.is_videos_sync_due("not-a-date", _now(), 2) is True
+    assert sync_trigger.is_videos_sync_due(12345, _now(), 2) is True  # non-str garbage
+
+
+def test_is_videos_sync_due_naive_finished_at():
+    naive = datetime.now(timezone.utc).replace(tzinfo=None) - timedelta(hours=3)
+    assert sync_trigger.is_videos_sync_due(naive.isoformat(), _now(), 2) is True
+
+
+def test_extract_finished_at():
+    assert sync_trigger._extract_finished_at(None) is None
+    assert sync_trigger._extract_finished_at("not json") is None
+    assert sync_trigger._extract_finished_at(json.dumps(["a"])) is None
+    assert sync_trigger._extract_finished_at(json.dumps({"status": "running", "finished_at": None})) is None
+    assert (
+        sync_trigger._extract_finished_at(json.dumps({"status": "completed", "finished_at": "2026-09-10T12:00:00+00:00"}))
+        == "2026-09-10T12:00:00+00:00"
+    )
+
+
+class _FakeDB:
+    def __init__(self):
+        self.closed = False
+
+    def close(self):
+        self.closed = True
+
+
+def _patch_threads(monkeypatch, started):
+    monkeypatch.setattr(
+        sync_trigger,
+        "threading",
+        SimpleNamespace(Thread=lambda target=None, daemon=None: started.append({"target": target, "daemon": daemon})),
+    )
+
+
+def test_maybe_trigger_skips_when_sync_running(monkeypatch):
+    started = []
+    monkeypatch.setattr(sync_trigger.sync, "is_videos_sync_running", lambda: True)
+    monkeypatch.setattr(
+        sync_trigger,
+        "SessionLocal",
+        lambda: (_ for _ in ()).throw(AssertionError("DB must not be touched while running")),
+    )
+    _patch_threads(monkeypatch, started)
+
+    sync_trigger.maybe_trigger_videos_sync()
+
+    assert started == []
+
+
+def test_maybe_trigger_skips_when_not_due(monkeypatch):
+    started = []
+    db = _FakeDB()
+    raw = json.dumps({"status": "completed", "finished_at": (_now() - timedelta(hours=1)).isoformat()})
+    monkeypatch.setattr(sync_trigger.sync, "is_videos_sync_running", lambda: False)
+    monkeypatch.setattr(sync_trigger, "SessionLocal", lambda: db)
+    monkeypatch.setattr(sync_trigger, "get_setting", lambda session, key: raw)
+    _patch_threads(monkeypatch, started)
+
+    sync_trigger.maybe_trigger_videos_sync()
+
+    assert started == []
+    assert db.closed is True
+
+
+def test_maybe_trigger_starts_thread_when_due_never_synced(monkeypatch):
+    started = []
+    db = _FakeDB()
+    monkeypatch.setattr(sync_trigger.sync, "is_videos_sync_running", lambda: False)
+    monkeypatch.setattr(sync_trigger, "SessionLocal", lambda: db)
+    monkeypatch.setattr(sync_trigger, "get_setting", lambda session, key: None)
+    _patch_threads(monkeypatch, started)
+
+    sync_trigger.maybe_trigger_videos_sync()
+
+    assert len(started) == 1
+    assert started[0]["target"] == sync_trigger._run_videos_sync
+    assert started[0]["daemon"] is True
+    assert db.closed is True
+
+
+def test_maybe_trigger_starts_thread_when_due_after_idle(monkeypatch):
+    started = []
+    db = _FakeDB()
+    raw = json.dumps({"status": "completed", "finished_at": (_now() - timedelta(hours=5)).isoformat()})
+    monkeypatch.setattr(sync_trigger.sync, "is_videos_sync_running", lambda: False)
+    monkeypatch.setattr(sync_trigger, "SessionLocal", lambda: db)
+    monkeypatch.setattr(sync_trigger, "get_setting", lambda session, key: raw)
+    _patch_threads(monkeypatch, started)
+
+    sync_trigger.maybe_trigger_videos_sync()
+
+    assert len(started) == 1
+    assert started[0]["daemon"] is True
+
+
+def test_maybe_trigger_never_raises_when_db_unavailable(monkeypatch):
+    started = []
+    monkeypatch.setattr(sync_trigger.sync, "is_videos_sync_running", lambda: False)
+    monkeypatch.setattr(
+        sync_trigger,
+        "SessionLocal",
+        lambda: (_ for _ in ()).throw(RuntimeError("db down")),
+    )
+    _patch_threads(monkeypatch, started)
+
+    sync_trigger.maybe_trigger_videos_sync()  # must not raise
+
+    assert started == []
+
+
+def test_run_videos_sync_swallows_sync_in_progress(monkeypatch):
+    closed = []
+    monkeypatch.setattr(
+        sync_trigger,
+        "SessionLocal",
+        lambda: SimpleNamespace(close=lambda: closed.append(True)),
+    )
+    monkeypatch.setattr(
+        sync_trigger.sync,
+        "sync_videos",
+        lambda db: (_ for _ in ()).throw(sync_trigger.sync.SyncInProgress("busy")),
+    )
+
+    sync_trigger._run_videos_sync()  # must not raise
+
+    assert closed == [True]