feat: optional topology per rack

- New topology option "Umfang": whole network (per site) and/or per
  rack, one landscape page each. Rack pages are grouped under
  "Topologie je Rack" with the rack titles one heading level lower to
  keep the table of contents short.
- Directly connected devices outside the rack are shown dimmed and
  dashed with their rack as subtitle, so uplinks stay visible.
- Cable paths are collected once per export and reused for all views.

Fix: devices from other sites were able to pull in their own neighbors
as external nodes; only direct neighbors of a group's devices are shown
now.

Bump version to 0.8.0.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

netbox_customer_export/forms.py

@@ -72,6 +72,13 @@ class ExportForm(forms.Form):
         widget=forms.CheckboxSelectMultiple,
         label="Beschriftung",
     )
+    topo_scope = forms.MultipleChoiceField(
+        choices=(("site", "Gesamtes Netzwerk (je Standort)"), ("rack", "Je Rack")),
+        initial=["site"],
+        required=False,
+        widget=forms.CheckboxSelectMultiple,
+        label="Umfang",
+    )
     topo_external = forms.BooleanField(
         required=False, initial=True, label="Provider-Leitungen & Geräte außerhalb anzeigen"
     )