chore: adopt the NAPALM driver standard

- CI moves to .gitea/workflows/ci.yml and calls the shared driver workflow
  of NAPALM/driver-standard; .github/ is gone.
- napalm-device-types >=4.21.1 from PyPI (the floor was 0.4.0).
- LICENSE, CHANGELOG, py.typed, SPDX license string, setuptools>=77,
  version floors on the dev extra (black is gone), links to git.netork.io;
  the README names Python 3.10 and the Gitea CI.
- mypy strict for the package; napalm_fritzbox.fritzbox is exempt for now
  (6 errors), recorded in the quality baseline with four long getters.
- Coverage floor 81 % (measured 81.36 %).

tests/quality_baseline.json

@@ -0,0 +1,20 @@
+{
+ "coverage_floor": 81.0,
+ "function_complexity": {
+  "napalm_fritzbox/fritzbox.py::FritzBoxDriver.get_interfaces": 12,
+  "napalm_fritzbox/fritzbox.py::FritzBoxDriver.get_port_forwards": 18,
+  "napalm_fritzbox/fritzbox.py::FritzBoxDriver.get_system_config": 15,
+  "napalm_fritzbox/fritzbox.py::FritzBoxDriver.get_wan_status": 12
+ },
+ "function_lines": {
+  "napalm_fritzbox/fritzbox.py::FritzBoxDriver.get_interfaces": 71,
+  "napalm_fritzbox/fritzbox.py::FritzBoxDriver.get_port_forwards": 72,
+  "napalm_fritzbox/fritzbox.py::FritzBoxDriver.get_system_config": 77,
+  "napalm_fritzbox/fritzbox.py::FritzBoxDriver.get_wan_status": 67
+ },
+ "mypy_relaxed": [
+  "napalm_fritzbox.fritzbox"
+ ],
+ "python_file_lines": {},
+ "untyped_public": []
+}