feat(schema): add bidirectional relationship identifiers and fabric-device links

- LocationSite: add devices (device__site) and fabrics (fabric__sites) reverse relationships
- InfraDevice.site: add identifier device__site
- InfraDevice: add fabric relationship (fabric__devices)
- InfraFabric.sites: add identifier fabric__sites; add devices reverse relationship (fabric__devices)
- InfraInterfaceVlan.vlan: add identifier vlan__svi
- InfraVLAN: add svi_interfaces reverse relationship (vlan__svi)
- Add 14-fabric-links.yml to assign all 10 devices to the evpn-lab fabric

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

infrahub/objects/14-fabric-links.yml

@@ -0,0 +1,28 @@
+# Fabric-to-Device links
+# Depends on: 02-devices, 03-fabric
+---
+apiVersion: infrahub.app/v1
+kind: Object
+spec:
+  kind: InfraDevice
+  data:
+    - name: spine1
+      fabric: "evpn-lab"
+    - name: spine2
+      fabric: "evpn-lab"
+    - name: leaf1
+      fabric: "evpn-lab"
+    - name: leaf2
+      fabric: "evpn-lab"
+    - name: leaf3
+      fabric: "evpn-lab"
+    - name: leaf4
+      fabric: "evpn-lab"
+    - name: leaf5
+      fabric: "evpn-lab"
+    - name: leaf6
+      fabric: "evpn-lab"
+    - name: leaf7
+      fabric: "evpn-lab"
+    - name: leaf8
+      fabric: "evpn-lab"