feat: add yang package init

Exports all YANG path classes for easy imports.

Part of #3

src/yang/__init__.py

@@ -0,0 +1,36 @@
+"""
+YANG module for Fabric Orchestrator.
+
+This module provides YANG path constants and utilities for
+managing Arista EVPN-VXLAN fabrics via gNMI.
+"""
+
+from .paths import (
+    Interfaces,
+    Loopbacks,
+    VLANs,
+    BGP,
+    AfiSafi,
+    VXLAN,
+    MLAG,
+    EVPN,
+    PortChannel,
+    System,
+    SubscriptionPath,
+    FabricSubscriptions,
+)
+
+__all__ = [
+    "Interfaces",
+    "Loopbacks",
+    "VLANs",
+    "BGP",
+    "AfiSafi",
+    "VXLAN",
+    "MLAG",
+    "EVPN",
+    "PortChannel",
+    "System",
+    "SubscriptionPath",
+    "FabricSubscriptions",
+]