Update PVideoDl to support custom download strategies and enhance cookie handling. Added new downloader registration system, updated README for clarity on downloaders, and introduced cookies configuration in settings. Frontend now includes a dedicated tab for download strategies and API endpoints for listing them.

tests/test_api.py

@@ -64,3 +64,12 @@ async def test_health(client):
     c, _ = client
     resp = await c.get("/api/health")
     assert resp.status_code == 200 and resp.json()["status"] == "ok"
+
+
+async def test_list_downloaders(client):
+    c, _ = client
+    resp = await c.get("/api/downloaders")
+    assert resp.status_code == 200
+    data = resp.json()
+    kinds = {d["kind"] for d in data}
+    assert "direct" in kinds and "fallback" in kinds  # встроенные httpx + yt-dlp