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>

api/calls.py

@@ -40,12 +40,7 @@ async def make_call(
             call_flow_id=request.call_flow_id,
             services=request.services,
         )
-        return CallResponse(
-            call_id=call.id,
-            status=call.status.value,
-            number=request.number,
-            mode=request.mode.value,
-        )
+        return CallResponse.from_call(call)
     except ValueError as e:
         raise HTTPException(status_code=400, detail=str(e))
     except Exception as e:
@@ -81,11 +76,8 @@ async def hold_slayer(
             call_flow_id=request.call_flow_id,
             device=request.transfer_to,
         )
-        return CallResponse(
-            call_id=call.id,
-            status="navigating_ivr",
-            number=request.number,
-            mode="hold_slayer",
+        return CallResponse.from_call(
+            call,
             message="Hold Slayer activated. I'll ring you when a human picks up. ☕",
         )
     except ValueError as e:
@@ -113,21 +105,7 @@ async def get_call(
     if not call:
         raise HTTPException(status_code=404, detail=f"Call {call_id} not found")
 
-    return CallStatusResponse(
-        call_id=call.id,
-        status=call.status.value,
-        direction=call.direction,
-        remote_number=call.remote_number,
-        mode=call.mode.value,
-        duration=call.duration,
-        hold_time=call.hold_time,
-        audio_type=call.current_classification.value,
-        intent=call.intent,
-        transcript_excerpt=call.transcript[-500:] if call.transcript else None,
-        classification_history=call.classification_history[-50:],
-        current_step=call.current_step_id,
-        services=call.services,
-    )
+    return CallStatusResponse.from_call(call)
 
 
 @router.post("/{call_id}/transfer")