Release a Windows-friendly runtime zip (v2.7.12)

The releases carried the wheel and the sdist; the only zip was GitHub's source
archive of the whole repository (tests, CI, tools).  A Windows user just wants
to extract a folder and double-click start.bat.

- scripts/build_release_zip.py builds simtrace-analyser-<version>.zip with a
  single top-level directory: the two Python packages, the PWA runtime files
  (frontend/tests and package.json stay out), the four launchers, the udev
  rule, the READMEs and the screenshot.  The .bat entries are written with
  CRLF line endings (cmd.exe mishandles bare-LF labels/goto), the .sh files
  keep their executable bit; LICENSE is included automatically once the repo
  has one.
- tests/test_release_zip.py pins the archive shape, the exclusions, the sw.js
  PRECACHE drift (every precached asset must travel), the CRLF/LF line endings
  and start.sh's mode.
- the release workflow builds the zip, checks it carries start.bat and the
  PWA, uploads it with the run and attaches it to the release.
- READMEs (EN/RU) and the release-notes template offer the zip as the
  Windows-friendly option; version 2.7.12, PWA cache v94.

Verified: the built zip (34 entries, 658 KB compressed) extracted and started
on Linux serves the same index.html; 553 Python + 80 Node tests.

README.md

@@ -105,7 +105,7 @@ Everything is on the
 **Wheel** (the PWA is inside the package):
 
 ```sh
-pip install ./simtrace_analyser-2.7.11-py3-none-any.whl
+pip install ./simtrace_analyser-2.7.12-py3-none-any.whl
 
 # then run (the UI is served at http://127.0.0.1:8081/):
 simtrace-analyser-server --capture gsmtap
@@ -119,7 +119,7 @@ Fedora), install into a virtual environment first:
 shown there):
 
 ```sh
-pip install https://github.com/anttro/simtrace-analyser/releases/download/v2.7.11/simtrace_analyser-2.7.11-py3-none-any.whl
+pip install https://github.com/anttro/simtrace-analyser/releases/download/v2.7.12/simtrace_analyser-2.7.12-py3-none-any.whl
 ```
 
 With the GitHub CLI, download the latest wheel without knowing the version:
@@ -133,6 +133,12 @@ pip install ./simtrace_analyser-*.whl
 without the git history: unzip, `cd` into it and use the launchers below
 (`./start.sh` on Linux/macOS, `start.bat` on Windows).
 
+**Zip (Windows-friendly, no installer)** — `simtrace-analyser-2.7.12.zip` is
+the runtime tree only (packages, PWA, launchers, docs; no tests, no git):
+download it, extract it anywhere and run `start.bat` (Windows) or
+`./start.sh` (Linux/macOS).  Python 3 has to be on `PATH`; `pip install pyusb`
+is only needed for direct SIMtrace2 capture.
+
 ### From a git clone (development)
 
 ```sh