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).

pyproject.toml

@@ -6,6 +6,7 @@ build-backend = "setuptools.build_meta"
 name = "pysim-simple-server"
 version = "3.31.0"
 description = "HTTP REST server wrapping pysim for the SIMple PWA"
+license = { text = "GPL-2.0-or-later" }
 requires-python = ">=3.8"
 # pysim is a git-only dependency installed explicitly by setup.bat/setup.sh.
 # Declaring it here would make pip resolve its full tree (including the SMPP
@@ -14,6 +15,9 @@ requires-python = ">=3.8"
 [project.scripts]
 pysim-simple-server = "pysim_simple_server.__main__:main"
 
+[tool.setuptools]
+license-files = ["LICENSE", "THIRD-PARTY-NOTICES"]
+
 [tool.setuptools.packages.find]
 include = ["pysim_simple_server*"]