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/app/models/__init__.py

@@ -1,4 +1,15 @@
 from app.models.auth_session import AuthSession
+from app.models.contact_session import ContactSession
+from app.models.entity import Entity
+from app.models.entity_sighting import EntitySighting
+from app.models.event import Event
 from app.models.user import User
 
-__all__ = ["User", "AuthSession"]
+__all__ = [
+    "User",
+    "AuthSession",
+    "ContactSession",
+    "Entity",
+    "EntitySighting",
+    "Event",
+]