Add NetBox-derived field switch topology (draw.io)

- export_topology.py: dumps switch + patch-panel cable graph from NetBox
  (Django shell, read-only)
- generate_drawio.py: renders topo_full.json as a draw.io diagram with
  natively-glued connectors (source/target by shape id, no hand-rolled
  glue formulas)
- topo_full.json + Field-Switch-Topology.drawio: current snapshot

Replaces the earlier hand-built .vsdx approach: plain-text format diffs
meaningfully in git, no Visio license needed to view/edit, and edges glue
natively instead of needing point-to-point formula hacks.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NM3nivbufxEWiKKmatEtEe

topology/export_topology.py

@@ -0,0 +1,68 @@
+"""
+Run INSIDE the NetBox Django shell to export the field-switch topology
+(switches + every patch panel / splice module they physically pass through)
+as JSON, for generate_drawio.py to render.
+
+Usage (from the NetBox host, e.g. /opt/netbox):
+
+    docker exec netbox-netbox-1 python3 /opt/netbox/netbox/manage.py shell \
+        -c "$(cat topology/export_topology.py)" 2>/dev/null > topology/topo_full.json
+
+The script only reads data -- it never modifies NetBox. If a switch's
+connected_endpoints comes back empty when it clearly shouldn't, that is a
+NetBox cable-path bug, not a bug in this script -- see the "gotchas" section
+of the repo README before assuming the physical link doesn't exist.
+"""
+from dcim.models import Device, Interface
+import json
+
+switch_ids = set(
+    Device.objects.filter(
+        role__slug__in=["core-switch", "dist-switch", "field-switch"]
+    ).values_list("id", flat=True)
+)
+
+ifaces = Interface.objects.filter(
+    device_id__in=switch_ids, cable__isnull=False
+).select_related("device")
+
+touched_devices = set(switch_ids)
+edges = set()  # (device_id_a, device_id_b), deduplicated, any two adjacent devices on a physical chain
+
+for i in ifaces:
+    path = i._path
+    if not path or not path.is_active:
+        continue
+    chain = []
+    for hop in i.trace():
+        for item in hop:
+            for t in item:
+                dev = getattr(t, "device", None)
+                if dev:
+                    if not chain or chain[-1] != dev.id:
+                        chain.append(dev.id)
+                    touched_devices.add(dev.id)
+    for a, b in zip(chain, chain[1:]):
+        if a != b:
+            edges.add(tuple(sorted((a, b))))
+
+devs = Device.objects.filter(id__in=touched_devices).select_related(
+    "site", "role", "device_type"
+)
+
+out = {
+    "devices": [
+        {
+            "id": d.id,
+            "name": d.name,
+            "role": d.role.slug,
+            "role_name": d.role.name,
+            "site": d.site.name if d.site else "",
+            "status": str(d.status),
+            "device_type": d.device_type.model,
+        }
+        for d in devs
+    ],
+    "edges": [[a, b] for a, b in sorted(edges)],
+}
+print(json.dumps(out))