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 README no longer installs
  it from git), py.typed, SPDX license string, setuptools>=77, version
  floors on the dev extra, Issues and Changelog links on git.netork.io.
- mypy strict for the package; napalm_bsd.base, napalm_bsd.freebsd and
  napalm_bsd.openbsd are exempt for now (28 errors, mostly getters typed
  as plain dicts rather than the device-types TypedDicts), recorded in the
  quality baseline with three complex parsers. parse.py is strict after a
  one-line annotation.
- Coverage floor 94 % (measured 94.63 %).

tests/quality_baseline.json

@@ -0,0 +1,16 @@
+{
+ "coverage_floor": 94.0,
+ "function_complexity": {
+  "napalm_bsd/parse.py::ifconfig": 21,
+  "napalm_bsd/parse.py::routes": 21,
+  "napalm_bsd/parse.py::users": 11
+ },
+ "function_lines": {},
+ "mypy_relaxed": [
+  "napalm_bsd.base",
+  "napalm_bsd.freebsd",
+  "napalm_bsd.openbsd"
+ ],
+ "python_file_lines": {},
+ "untyped_public": []
+}