feat(netbox): Add NetBox API client for fabric intent retrieval

Implements FabricNetBoxClient using pynetbox to fetch:
- Device and interface data
- BGP sessions and peer groups (plugin)
- L2VPN/EVPN VNI mappings
- VRF and route target configuration
- MLAG custom fields

Relates to #5

src/netbox/__init__.py

@@ -0,0 +1,36 @@
+"""
+NetBox Client Module for Fabric Orchestrator.
+
+This module provides a NetBox API client for fetching fabric intent data
+using pynetbox.
+
+Usage:
+    from src.netbox import FabricNetBoxClient
+
+    client = FabricNetBoxClient(
+        url="http://netbox.local",
+        token="your-token"
+    )
+
+    # Get all leaf devices
+    leaves = client.get_leaf_devices()
+
+    # Get complete intent for a device
+    intent = client.get_device_intent("leaf1")
+"""
+
+from .client import (
+    FabricNetBoxClient,
+    NetBoxAPIError,
+    NetBoxConnectionError,
+    NetBoxError,
+    NetBoxNotFoundError,
+)
+
+__all__ = [
+    "FabricNetBoxClient",
+    "NetBoxError",
+    "NetBoxConnectionError",
+    "NetBoxNotFoundError",
+    "NetBoxAPIError",
+]