feat: add initial Hold Slayer AI telephony gateway implementation

Complete project scaffolding and core implementation of an AI-powered
telephony system that calls companies, navigates IVR menus, waits on
hold, and transfers to the user when a human answers.

Key components:
- FastAPI server with REST API, WebSocket, and MCP (SSE) interfaces
- SIP/VoIP call management via PJSUA2 with RTP audio streaming
- LLM-powered IVR navigation using OpenAI/Anthropic with tool calling
- Hold detection service combining audio analysis and silence detection
- Real-time STT (Whisper/Deepgram) and TTS (OpenAI/Piper) pipelines
- Call recording with per-channel and mixed audio capture
- Event bus (asyncio pub/sub) for real-time client updates
- Web dashboard with live call monitoring
- SQLite persistence via SQLAlchemy with call history and analytics
- Notification support (email, SMS, webhook, desktop)
- Docker Compose deployment with Opal VoIP and Opal Media containers
- Comprehensive test suite with unit, integration, and E2E tests
- Simplified .gitignore and full project documentation in README

tests/test_call_flows.py

@@ -0,0 +1,173 @@
+"""
+Tests for call flow models and serialization.
+"""
+
+import pytest
+
+from models.call_flow import ActionType, CallFlow, CallFlowCreate, CallFlowStep, CallFlowSummary
+
+
+class TestCallFlowStep:
+    """Test CallFlowStep model."""
+
+    def test_basic_dtmf_step(self):
+        step = CallFlowStep(
+            id="press_1",
+            description="Press 1 for English",
+            action=ActionType.DTMF,
+            action_value="1",
+            expect="for english|para español",
+            next_step="main_menu",
+        )
+        assert step.id == "press_1"
+        assert step.action == ActionType.DTMF
+        assert step.action_value == "1"
+        assert step.timeout == 30  # default
+
+    def test_hold_step(self):
+        step = CallFlowStep(
+            id="hold_queue",
+            description="On hold waiting for agent",
+            action=ActionType.HOLD,
+            timeout=7200,
+            next_step="agent_connected",
+            notes="Average hold: 25-45 min. Plays Vivaldi. Kill me.",
+        )
+        assert step.action == ActionType.HOLD
+        assert step.timeout == 7200
+        assert "Vivaldi" in step.notes
+
+    def test_transfer_step(self):
+        step = CallFlowStep(
+            id="connected",
+            description="Agent picked up!",
+            action=ActionType.TRANSFER,
+            action_value="sip_phone",
+        )
+        assert step.action == ActionType.TRANSFER
+
+
+class TestCallFlow:
+    """Test CallFlow model."""
+
+    @pytest.fixture
+    def sample_flow(self):
+        return CallFlow(
+            id="test-bank",
+            name="Test Bank - Main Line",
+            phone_number="+18005551234",
+            description="Test bank IVR",
+            steps=[
+                CallFlowStep(
+                    id="greeting",
+                    description="Language selection",
+                    action=ActionType.DTMF,
+                    action_value="1",
+                    expect="for english",
+                    next_step="main_menu",
+                ),
+                CallFlowStep(
+                    id="main_menu",
+                    description="Main menu",
+                    action=ActionType.LISTEN,
+                    next_step="agent_request",
+                    fallback_step="agent_request",
+                ),
+                CallFlowStep(
+                    id="agent_request",
+                    description="Request agent",
+                    action=ActionType.DTMF,
+                    action_value="0",
+                    next_step="hold_queue",
+                ),
+                CallFlowStep(
+                    id="hold_queue",
+                    description="Hold queue",
+                    action=ActionType.HOLD,
+                    timeout=3600,
+                    next_step="agent_connected",
+                ),
+                CallFlowStep(
+                    id="agent_connected",
+                    description="Agent connected",
+                    action=ActionType.TRANSFER,
+                    action_value="sip_phone",
+                ),
+            ],
+            tags=["bank", "personal"],
+            avg_hold_time=2100,
+            success_rate=0.92,
+        )
+
+    def test_step_count(self, sample_flow):
+        assert len(sample_flow.steps) == 5
+
+    def test_get_step(self, sample_flow):
+        step = sample_flow.get_step("hold_queue")
+        assert step is not None
+        assert step.action == ActionType.HOLD
+        assert step.timeout == 3600
+
+    def test_get_step_not_found(self, sample_flow):
+        assert sample_flow.get_step("nonexistent") is None
+
+    def test_first_step(self, sample_flow):
+        first = sample_flow.first_step()
+        assert first is not None
+        assert first.id == "greeting"
+
+    def test_steps_by_id(self, sample_flow):
+        steps = sample_flow.steps_by_id()
+        assert len(steps) == 5
+        assert "greeting" in steps
+        assert "agent_connected" in steps
+        assert steps["agent_connected"].action == ActionType.TRANSFER
+
+    def test_serialization_roundtrip(self, sample_flow):
+        """Test JSON serialization and deserialization."""
+        json_str = sample_flow.model_dump_json()
+        restored = CallFlow.model_validate_json(json_str)
+        assert restored.id == sample_flow.id
+        assert len(restored.steps) == len(sample_flow.steps)
+        assert restored.steps[0].id == "greeting"
+        assert restored.avg_hold_time == 2100
+
+
+class TestCallFlowCreate:
+    """Test call flow creation model."""
+
+    def test_minimal_create(self):
+        create = CallFlowCreate(
+            name="My Bank",
+            phone_number="+18005551234",
+            steps=[
+                CallFlowStep(
+                    id="start",
+                    description="Start",
+                    action=ActionType.HOLD,
+                    next_step="end",
+                ),
+            ],
+        )
+        assert create.name == "My Bank"
+        assert len(create.steps) == 1
+        assert create.tags == []
+        assert create.notes is None
+
+
+class TestCallFlowSummary:
+    """Test lightweight summary model."""
+
+    def test_summary(self):
+        summary = CallFlowSummary(
+            id="chase-bank-main",
+            name="Chase Bank - Main",
+            phone_number="+18005551234",
+            step_count=6,
+            avg_hold_time=2100,
+            success_rate=0.92,
+            times_used=15,
+            tags=["bank"],
+        )
+        assert summary.step_count == 6
+        assert summary.success_rate == 0.92