feat: add call history API endpoints and TTS service client

Adds read-only access to persisted call records for the dashboard
and implements a client for the Rhema text-to-speech service.

- api/call_history.py: New router providing paged call lists
  and detailed call records with transcript metadata.
- services/tts.py: Async client for OpenAI-compatible TTS
  endpoints (Rhema/Kokoro) used for call-flow steps.

tests/test_receptionist.py

@@ -0,0 +1,74 @@
+"""Tests for the AI Receptionist decision logic (services/receptionist.py)."""
+
+from types import SimpleNamespace
+
+import pytest
+
+from config import ReceptionistSettings, Settings
+from models.routing import (
+    RoutingAction,
+    RoutingActionType,
+    RoutingDecision,
+)
+from services.receptionist import ReceptionistService
+
+
+def _make_gateway():
+    settings = Settings()
+    settings.receptionist = ReceptionistSettings()
+    return SimpleNamespace(settings=settings, devices={})
+
+
+class TestReceptionistDecide:
+    def test_rule_wins_over_llm_when_rule_is_actionable(self):
+        gw = _make_gateway()
+        svc = ReceptionistService(gw)
+        rule_action = RoutingAction(type=RoutingActionType.REJECT, message="nope")
+        decision = RoutingDecision(action=rule_action, reason="rule said so")
+        chosen = svc._decide(decision, {"recommended_action": "ring"})
+        assert chosen.type == RoutingActionType.REJECT
+
+    def test_falls_back_to_llm_when_rule_is_default_take_message(self):
+        gw = _make_gateway()
+        svc = ReceptionistService(gw)
+        decision = RoutingDecision(
+            action=RoutingAction(type=RoutingActionType.TAKE_MESSAGE),
+            reason="default",
+        )
+        chosen = svc._decide(decision, {"recommended_action": "ring"})
+        assert chosen.type == RoutingActionType.RING_CHAIN
+
+    def test_llm_reject_recommendation_is_honored(self):
+        gw = _make_gateway()
+        svc = ReceptionistService(gw)
+        chosen = svc._decide(None, {"recommended_action": "reject"})
+        assert chosen.type == RoutingActionType.REJECT
+        assert chosen.message  # should carry a polite decline message
+
+
+class TestReceptionistDeviceList:
+    def test_ring_device_returns_explicit_device(self):
+        gw = _make_gateway()
+        svc = ReceptionistService(gw)
+        action = RoutingAction(type=RoutingActionType.RING_DEVICE, device_id="dev_a")
+        assert svc._resolve_device_list(action, {}) == ["dev_a"]
+
+    def test_ring_chain_uses_action_list_when_present(self):
+        gw = _make_gateway()
+        svc = ReceptionistService(gw)
+        action = RoutingAction(
+            type=RoutingActionType.RING_CHAIN,
+            device_ids=["dev_a", "dev_b"],
+        )
+        assert svc._resolve_device_list(action, {}) == ["dev_a", "dev_b"]
+
+
+class TestFrameSilenceHeuristic:
+    def test_zeroes_are_silent(self):
+        # 16-bit PCM zeros → silent
+        assert ReceptionistService._frame_is_silent(b"\x00\x00" * 80) is True
+
+    def test_loud_pattern_not_silent(self):
+        # Loud values → not silent
+        loud = b"\xff\x7f" * 80  # max int16 every sample
+        assert ReceptionistService._frame_is_silent(loud) is False