feat: license export compatible with NetBox-SLM

When the netbox_slm plugin is installed, the "Lizenzen" section reads
its SoftwareLicense objects automatically:

- Scope matching via installations on devices, VMs or clusters in the
  exported site/location/tenant, plus licenses assigned to the tenant
  and tenant-less licenses of its tenant group (incl. parent groups) or,
  for tenant group exports, of the group and its subgroups.
- One table per manufacturer: license, product/version, type, amount,
  validity incl. renewal interval, status (active, expires in N days,
  expired, lifetime), support, installation target and tenant.
- License keys only with the "include secrets" option.
- Other configured license_sources keep working alongside.

Table cells in HTML/PDF now preserve line breaks.

Bump version to 0.9.0.

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

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "netbox-customer-export"
-version = "0.8.0"
+version = "0.9.0"
 description = "NetBox-Plugin: Kundendokumentation (PDF/Word) für Standorte, Lokationen, Mandanten und Mandantengruppen"
 readme = "README.md"
 requires-python = ">=3.10"