license: GPL-2.0-or-later, matching pysim

The server imports pySim (GPL-2.0-or-later - its source headers carry the
"or later" clause), and the PWA's EF decoders were ported/adapted from
simtrace-analyser (also GPL-2.0-or-later), so the whole repository is
distributed under the same license.  Not bundling pysim changes only what
we redistribute (none of pysim's code - setup fetches it from upstream),
not the license of our own code.

- LICENSE: the GPL-2 text (the copy pysim distributes).
- pyproject: license = GPL-2.0-or-later + license-files, so the wheel
  carries LICENSE and THIRD-PARTY-NOTICES in .dist-info/licenses/.
- THIRD-PARTY-NOTICES: pysim is a runtime dependency (not included); the
  bundled MIT components keep their notices with the exact upstream
  copyright lines (mcc-mnc-list, aes-js 3.1.2, des.js 1.1.0).
- READMEs: a License section (EN/RU) pointing at the above.

No functional change: 953 frontend + 989 Python green.  The wheel
metadata was verified with pip wheel (License: GPL-2.0-or-later, both
license files present).

README.md

@@ -788,3 +788,17 @@ See [docs/api.md](docs/api.md) for the full endpoint reference.
 | any | newer major | ⚠️ Server newer — update PWA |
 
 The PWA checks the server version on connect via `GET /api/version` and compares the major version (e.g. a 3.x PWA with a 3.x server; a 2.x server is flagged as outdated).
+
+## License
+
+**GPL-2.0-or-later** — see [LICENSE](LICENSE). This is the same license as
+[pySim](https://github.com/osmocom/pysim), whose library the server imports, and
+as [simtrace-analyser](https://github.com/anttro/simtrace-analyser), from which
+some client-side decoders were ported.
+
+pySim itself is not included in this repository or in the release artifacts:
+`setup.sh` / `setup.bat` install it from its upstream git repository.
+
+Bundled third-party components (the MCC/MNC operator list and the AES/DES
+bundles in the PWA) keep their own MIT licenses — see
+[THIRD-PARTY-NOTICES](THIRD-PARTY-NOTICES).