refactor: composition root in lifespan, break core↔services cycle, shared data layer

The gateway was the composition root, device registry, inbound-call
policy, and call-operations service in one class, with core↔services
circular imports papered over by function-local imports, wiring done
by assigning private attributes, and MCP tools duplicating REST query
logic against their own sessions.

Composition:
- main.py's lifespan now builds every service and wires them by
  constructor/registration. gateway.from_config() is gone; core/ no
  longer imports services/ anywhere — the cycle is dead.
- Inbound-call policy moved to ReceptionistService.on_inbound_call
  (routing evaluation, reject/answer, screening dispatch); wired as
  the engine's on_incoming_call by the lifespan. Receptionist deps
  (tts/transcription/recording/routing) are constructor-injected —
  no more gateway._tts reach-through or importing hold_slayer's
  private _get_llm (now services.llm_client.get_llm, shared).
- Hold-slayer launch goes through a mode-handler registry
  (register_mode_handler); the gateway no longer knows the service's
  type. CallManager takes on_call_ended in its constructor.
- build_sip_engine() is a pure function taking explicit callbacks.
- api/routing.py uses the routing service from app.state via a
  proper dependency instead of gateway._routing.

Shared data layer:
- db.session_scope() is the one session convention (get_db wraps it).
- services/call_persistence.py gains the query/write functions and
  the single StoredCallFlow→CallFlow mapper; api/call_flows.py,
  api/call_history.py, and the six DB-touching MCP tools are thin
  wrappers over them — the two surfaces can't drift.
- legs_for_call() replaces the three private _call_legs scans
  (gateway transfer/hangup, REST dtmf, MCP dtmf).

7 new tests (mode-handler launch, on_call_ended hook, receptionist
inbound answer/reject, call-flow CRUD round-trip and history routes
against real SQLite through the shared layer). aiosqlite added to dev
deps for that.

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

api/call_flows.py

@@ -2,26 +2,21 @@
 Call Flows API — Store and manage IVR navigation trees.
 
 The system gets smarter every time you call somewhere.
+Thin HTTP layer over the shared data functions in call_persistence.
 """
 
-import uuid
-from datetime import datetime
-
 from fastapi import APIRouter, Depends, HTTPException
 from slugify import slugify
-from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
-from api.deps import get_gateway
-from core.gateway import AIPSTNGateway
-from db.database import StoredCallFlow, get_db
+from db.database import get_db
 from models.call_flow import (
     CallFlow,
     CallFlowCreate,
-    CallFlowStep,
     CallFlowSummary,
     CallFlowUpdate,
 )
+from services import call_persistence as store
 
 router = APIRouter()
 
@@ -34,39 +29,23 @@ async def create_call_flow(
     """Store a new call flow for a phone number."""
     flow_id = slugify(flow.name)
 
-    # Check if ID already exists
-    existing = await db.execute(
-        select(StoredCallFlow).where(StoredCallFlow.id == flow_id)
-    )
-    if existing.scalar_one_or_none():
+    if await store.get_flow(db, flow_id):
         raise HTTPException(
             status_code=409,
             detail=f"Call flow '{flow_id}' already exists. Use PUT to update.",
         )
 
-    db_flow = StoredCallFlow(
-        id=flow_id,
+    row = await store.create_flow(
+        db,
+        flow_id=flow_id,
         name=flow.name,
         phone_number=flow.phone_number,
         description=flow.description,
         steps=[s.model_dump() for s in flow.steps],
         tags=flow.tags,
         notes=flow.notes,
-        last_verified=datetime.now(),
-    )
-    db.add(db_flow)
-    await db.flush()
-
-    return CallFlow(
-        id=flow_id,
-        name=flow.name,
-        phone_number=flow.phone_number,
-        description=flow.description,
-        steps=flow.steps,
-        tags=flow.tags,
-        notes=flow.notes,
-        last_verified=datetime.now(),
     )
+    return store.flow_to_model(row)
 
 
 @router.get("/", response_model=list[CallFlowSummary])
@@ -74,9 +53,7 @@ async def list_call_flows(
     db: AsyncSession = Depends(get_db),
 ):
     """List all stored call flows."""
-    result = await db.execute(select(StoredCallFlow))
-    rows = result.scalars().all()
-
+    rows = await store.list_flows(db)
     return [
         CallFlowSummary(
             id=row.id,
@@ -100,26 +77,10 @@ async def get_call_flow(
     db: AsyncSession = Depends(get_db),
 ):
     """Get a stored call flow by ID."""
-    result = await db.execute(
-        select(StoredCallFlow).where(StoredCallFlow.id == flow_id)
-    )
-    row = result.scalar_one_or_none()
+    row = await store.get_flow(db, flow_id)
     if not row:
         raise HTTPException(status_code=404, detail=f"Call flow '{flow_id}' not found")
-
-    return CallFlow(
-        id=row.id,
-        name=row.name,
-        phone_number=row.phone_number,
-        description=row.description or "",
-        steps=[CallFlowStep(**s) for s in row.steps],
-        tags=row.tags or [],
-        notes=row.notes,
-        avg_hold_time=row.avg_hold_time,
-        success_rate=row.success_rate,
-        last_used=row.last_used,
-        times_used=row.times_used or 0,
-    )
+    return store.flow_to_model(row)
 
 
 @router.get("/by-number/{phone_number}", response_model=CallFlow)
@@ -128,29 +89,13 @@ async def get_flow_for_number(
     db: AsyncSession = Depends(get_db),
 ):
     """Look up stored call flow by phone number."""
-    result = await db.execute(
-        select(StoredCallFlow).where(StoredCallFlow.phone_number == phone_number)
-    )
-    row = result.scalar_one_or_none()
+    row = await store.get_flow_by_number(db, phone_number)
     if not row:
         raise HTTPException(
             status_code=404,
             detail=f"No call flow found for {phone_number}",
         )
-
-    return CallFlow(
-        id=row.id,
-        name=row.name,
-        phone_number=row.phone_number,
-        description=row.description or "",
-        steps=[CallFlowStep(**s) for s in row.steps],
-        tags=row.tags or [],
-        notes=row.notes,
-        avg_hold_time=row.avg_hold_time,
-        success_rate=row.success_rate,
-        last_used=row.last_used,
-        times_used=row.times_used or 0,
-    )
+    return store.flow_to_model(row)
 
 
 @router.put("/{flow_id}", response_model=CallFlow)
@@ -160,10 +105,7 @@ async def update_call_flow(
     db: AsyncSession = Depends(get_db),
 ):
     """Update an existing call flow."""
-    result = await db.execute(
-        select(StoredCallFlow).where(StoredCallFlow.id == flow_id)
-    )
-    row = result.scalar_one_or_none()
+    row = await store.get_flow(db, flow_id)
     if not row:
         raise HTTPException(status_code=404, detail=f"Call flow '{flow_id}' not found")
 
@@ -181,20 +123,7 @@ async def update_call_flow(
         row.last_verified = update.last_verified
 
     await db.flush()
-
-    return CallFlow(
-        id=row.id,
-        name=row.name,
-        phone_number=row.phone_number,
-        description=row.description or "",
-        steps=[CallFlowStep(**s) for s in row.steps],
-        tags=row.tags or [],
-        notes=row.notes,
-        avg_hold_time=row.avg_hold_time,
-        success_rate=row.success_rate,
-        last_used=row.last_used,
-        times_used=row.times_used or 0,
-    )
+    return store.flow_to_model(row)
 
 
 @router.delete("/{flow_id}")
@@ -203,10 +132,7 @@ async def delete_call_flow(
     db: AsyncSession = Depends(get_db),
 ):
     """Delete a stored call flow."""
-    result = await db.execute(
-        select(StoredCallFlow).where(StoredCallFlow.id == flow_id)
-    )
-    row = result.scalar_one_or_none()
+    row = await store.get_flow(db, flow_id)
     if not row:
         raise HTTPException(status_code=404, detail=f"Call flow '{flow_id}' not found")