feat: spirit engine — seance WS, entity minting/Codex, Piper TTS voices, wire telemetry

- WS /ws/session: modes, summon, anomaly fragments, streaming direct contact,
  passive wire-ghost ambient loop, per-user rate limits, event transcript
- entities: anomaly-signature fingerprinting, LLM minting + procedural
  fallback, Codex matching with contact counts and sightings
- tts: 8 local Piper voices (EN/ES), per-entity voice profiles, numpy
  effects chain (pitch/rate/bitcrush/echo/static)
- llm: streaming client, submit_stream in bounded queue, SpiritService
  with offline fallbacks for every channel
- routes: public /api/codex, /api/codex/{id}, /api/stats; /audio static mount
- models: Entity, EntitySighting, Event, ContactSession(entity_id, language)

backend/tests/conftest.py

@@ -1,4 +1,6 @@
+import pytest
 import pytest_asyncio
+from fastapi.testclient import TestClient
 from httpx import ASGITransport, AsyncClient
 from sqlalchemy.ext.asyncio import async_sessionmaker, create_async_engine
 from sqlalchemy.pool import NullPool
@@ -37,3 +39,25 @@ async def client():
     transport = ASGITransport(app=app)
     async with AsyncClient(transport=transport, base_url="https://test") as ac:
         yield ac
+
+
+@pytest.fixture
+def sync_client(monkeypatch):
+    """Sync TestClient (supports WebSocket tests). The WS handler's session
+    maker is swapped to the NullPool test engine so its writes land in the
+    same test database the async fixtures see. The lifespan's engine is also
+    swapped: TestClient runs the lifespan on its own portal loop, and the
+    pooled production engine would carry connections across loops."""
+    import app.main as main_module
+    import app.ws as ws_module
+
+    monkeypatch.setattr(ws_module, "session_maker", TestSessionLocal)
+    monkeypatch.setattr(main_module, "engine", test_engine)
+    with TestClient(app, base_url="https://testserver") as tc:
+        yield tc
+
+
+@pytest_asyncio.fixture
+async def db_session():
+    async with TestSessionLocal() as session:
+        yield session