feat: add public index page with censored playlist and live reveals

Public-facing page at / shows the current show's playlist with tracks
obscured until the admin marks them as announced. Tracks reveal in
real-time via a new unauthenticated /ws/public WebSocket. Server-side
censorship on /public/playlist strips track details from unannounced
items and sanitizes announced tracks to only expose frontend-needed
fields (no raw_json, track_id, etc). Past episodes are browsable with
fully revealed but sanitized tracklists.

Also fixes RuntimeError on backfill shutdown by closing the httpx
client on the same event loop that created it.

Made-with: Cursor

tests/test_websocket.py

@@ -1,5 +1,5 @@
 import pytest
-from ntr_fetcher.websocket import AnnounceManager
+from ntr_fetcher.websocket import AnnounceManager, PublicManager
 
 
 @pytest.fixture
@@ -98,3 +98,61 @@ async def test_status_broadcast_includes_clients(manager):
         assert msg["subscribers"] == 1
         assert len(msg["clients"]) == 1
         assert msg["clients"][0]["client_id"] == "my-bot"
+
+
+# --- PublicManager tests ---
+
+
+@pytest.fixture
+def public_manager():
+    return PublicManager()
+
+
+def test_public_no_clients_initially(public_manager):
+    assert public_manager.client_count == 0
+
+
+@pytest.mark.asyncio
+async def test_public_add_remove_client(public_manager):
+    class FakeWS:
+        async def send_json(self, data):
+            pass
+
+    ws = FakeWS()
+    public_manager.add_client(ws)
+    assert public_manager.client_count == 1
+
+    public_manager.remove_client(ws)
+    assert public_manager.client_count == 0
+
+
+@pytest.mark.asyncio
+async def test_public_broadcast(public_manager):
+    received = []
+
+    class FakeWS:
+        async def send_json(self, data):
+            received.append(data)
+
+    ws1 = FakeWS()
+    ws2 = FakeWS()
+    public_manager.add_client(ws1)
+    public_manager.add_client(ws2)
+
+    await public_manager.broadcast({"type": "reveal", "position": 1})
+    assert len(received) == 2
+    assert all(m["type"] == "reveal" for m in received)
+
+
+@pytest.mark.asyncio
+async def test_public_broadcast_removes_dead_clients(public_manager):
+    class DeadWS:
+        async def send_json(self, data):
+            raise Exception("closed")
+
+    ws = DeadWS()
+    public_manager.add_client(ws)
+    assert public_manager.client_count == 1
+
+    await public_manager.broadcast({"type": "reveal", "position": 1})
+    assert public_manager.client_count == 0