Release-Skript mit automatischer Versionierung und Docker-Builds

- scripts/release.py: Version (patch/minor/major) automatisch hochzaehlen, CHANGELOG
  abschliessen, committen, taggen; --build baut alle Pakete in Docker
- docker-build/: Build-Container fuer Windows (Wine + PyInstaller + Inno Setup),
  Linux und Android; Server-Image als docker-save-Archiv
- Versionsanzeige im Desktop-Client und in der Android-App
- Feste Android-Release-Signatur aus secrets/ (nicht im Git)
- Windows-Icon im Repo, damit der Wine-Build ohne Qt-Fenster auskommt

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docker-build/windows.Dockerfile

@@ -0,0 +1,12 @@
+# Build-Umgebung fuer den Windows-Client: Windows-Python + PyInstaller + Inno Setup unter Wine
+FROM tobix/pywine:3.12
+ARG INNO_VERSION=6.7.3
+RUN apt-get update && apt-get install -y --no-install-recommends xvfb xauth wget zip && rm -rf /var/lib/apt/lists/* \
+ && wget -q https://github.com/jrsoftware/issrc/releases/download/is-$(echo ${INNO_VERSION} | tr . _)/innosetup-${INNO_VERSION}.exe -O /tmp/is.exe \
+ && xvfb-run -a wine /tmp/is.exe /VERYSILENT /SUPPRESSMSGBOXES /NORESTART /SP- /ALLUSERS \
+ && rm /tmp/is.exe && wineserver -w
+COPY client-desktop/requirements.txt docker-build/windows-constraints.txt /tmp/
+RUN wine python -m pip install --no-cache-dir -r Z:/tmp/requirements.txt -c Z:/tmp/windows-constraints.txt pyinstaller \
+ && wineserver -w
+COPY docker-build/build-windows.sh docker-build/windows-constraints.txt /usr/local/bin/
+CMD ["sh", "/usr/local/bin/build-windows.sh"]