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

models/contact.py

@@ -0,0 +1,60 @@
+"""
+Contact models — People and organizations you call.
+"""
+
+from datetime import datetime
+from typing import Optional
+
+from pydantic import BaseModel, Field
+
+
+class PhoneNumber(BaseModel):
+    """A phone number associated with a contact."""
+
+    number: str  # E.164 format
+    label: str = "main"  # main, mobile, work, home, fax, etc.
+    primary: bool = False
+
+
+class ContactBase(BaseModel):
+    """Shared contact fields."""
+
+    name: str
+    phone_numbers: list[PhoneNumber]
+    category: Optional[str] = None  # personal / business / service
+    routing_preference: Optional[str] = None  # how to handle their calls
+    notes: Optional[str] = None
+
+
+class Contact(ContactBase):
+    """Full contact model."""
+
+    id: str
+    call_count: int = 0
+    last_call: Optional[datetime] = None
+    created_at: Optional[datetime] = None
+    updated_at: Optional[datetime] = None
+
+    @property
+    def primary_number(self) -> Optional[str]:
+        """Get the primary phone number."""
+        for pn in self.phone_numbers:
+            if pn.primary:
+                return pn.number
+        return self.phone_numbers[0].number if self.phone_numbers else None
+
+
+class ContactCreate(ContactBase):
+    """Request model for creating a contact."""
+
+    pass
+
+
+class ContactUpdate(BaseModel):
+    """Request model for updating a contact."""
+
+    name: Optional[str] = None
+    phone_numbers: Optional[list[PhoneNumber]] = None
+    category: Optional[str] = None
+    routing_preference: Optional[str] = None
+    notes: Optional[str] = None