feat: configuration loading and netbox api client

config.yaml next to the script (or $NETBOX_INVENTORY_CONFIG) with environment
variable overrides, requests session with token auth, paginated list fetching
and readable error reporting.

config.yaml.example

@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+# Copyright (C) 2026 Bryan Joshua Pedini
+
+netbox:
+  url: "https://netbox.example.com"
+  token: "0123456789abcdef0123456789abcdef01234567"
+  verify_ssl: true
+  timeout: 30
+
+inventory:
+  # where to get the hosts from: ip-addresses | virtual-machines
+  source: "ip-addresses"
+  # optional filter, see README.md for the full list
+  filter: ""
+  filter_value: ""