Stage 5: Alembic migrations, durable call rows, one transcript truth

Alembic replaces create_all as the schema authority: async env.py
against Base.metadata (CLI and in-app entry paths share it via
config.attributes["connection"]), an autogenerated baseline of the
create_all-era schema, and init_db now runs upgrade head — stamping
the baseline first on a pre-Alembic database so existing deployments
adopt cleanly. create_all remains for tests only.

Calls are durable from the start: CallManager gains an
on_call_created hook (wired to persist_call_on_create) that inserts
an in_progress CallRecord the moment a call is created;
persist_call_on_end finalizes that same row. A SIGKILL mid-call now
leaves an in_progress row instead of erasing the call from history
(verified live against the dev database).

One transcript representation: ActiveCall.transcript_chunks holds
TranscriptEntry (t_offset_ms, speaker, text) — add_transcript stamps
real offsets from connect time, receptionist passes speaker instead
of encoding it into "caller: ..." strings, persisted chunks carry
real seek offsets, and the dead CallRecord.transcript Text column is
dropped by migration. Device.is_online migrates String → Boolean
(with a USING cast for existing rows).

Model de-triplication: CallResponse/CallStatusResponse build via
from_call classmethods (one ActiveCall→response mapping);
DeviceStatus deleted — can_receive_call is a computed field on
Device and the list endpoint returns the domain model; all row↔dict
and row↔domain mapping now lives in call_persistence.py
(record_summary/record_detail/chunk_to_dict + device row functions).

New tests/test_data_layer.py: upgrade-head-matches-models,
pre-Alembic adoption, durable in_progress rows, end-without-create
fallback, transcript offsets, consolidated response models.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

main.py

@@ -26,7 +26,7 @@ from db.database import close_db, init_db
 from mcp_server.server import create_mcp_server
 from models.call import CallMode
 from services.audio_classifier import AudioClassifier
-from services.call_persistence import persist_call_on_end
+from services.call_persistence import persist_call_on_create, persist_call_on_end
 from services.hold_slayer import HoldSlayerService
 from services.notification import NotificationService
 from services.receptionist import ReceptionistService
@@ -139,7 +139,11 @@ async def lifespan(app: FastAPI):
         # === Composition root ===
         # Build the gateway and every service here, wiring them by
         # constructor/registration — nothing constructs its own deps.
-        gateway = AIPSTNGateway(settings=settings, on_call_ended=persist_call_on_end)
+        gateway = AIPSTNGateway(
+            settings=settings,
+            on_call_created=persist_call_on_create,
+            on_call_ended=persist_call_on_end,
+        )
 
         classifier = AudioClassifier(settings.classifier)
         transcription = TranscriptionService(settings.speaches)