Add Flet desktop client

Client/Packaging/BuildAppImage.sh

@@ -0,0 +1,38 @@
+#!/bin/bash
+# Builds dist/SaraView-x86_64.AppImage: a PyInstaller one-file build (with
+# the font and icon bundled) wrapped by appimagetool, the same way SaraSort's,
+# SaraSuite's and SaraFem's AppImages are made. Needs appimagetool on PATH.
+set -euo pipefail
+cd "$(dirname "$(readlink -f "$0")")/.."
+
+[ -d .venv ] || python3 -m venv .venv
+.venv/bin/pip install --quiet --disable-pip-version-check -r requirements.txt pyinstaller
+
+# --collect-data flet: without it ft.Icons crashes when frozen.
+.venv/bin/pyinstaller --noconfirm --clean --log-level WARN \
+    --onefile --windowed --name SaraView --collect-data flet \
+    --add-data "$PWD/assets:assets" \
+    --distpath build/PyInstaller/dist --workpath build/PyInstaller/work --specpath build/PyInstaller \
+    "$PWD/Main.py"
+
+AppDir=build/AppDir
+rm -rf "$AppDir"
+mkdir -p "$AppDir/usr/bin"
+cp build/PyInstaller/dist/SaraView "$AppDir/usr/bin/SaraView"
+ln -s usr/bin/SaraView "$AppDir/AppRun"
+cp assets/Icon.png "$AppDir/SaraView.png"
+ln -s SaraView.png "$AppDir/.DirIcon"
+cat > "$AppDir/SaraView.desktop" << DESKTOP
+[Desktop Entry]
+Type=Application
+Name=SaraView
+Comment=View and edit files, locally or on a SaraView server
+Exec=SaraView
+Icon=SaraView
+Terminal=false
+Categories=Utility;
+DESKTOP
+
+mkdir -p dist
+ARCH=x86_64 appimagetool --no-appstream "$AppDir" dist/SaraView-x86_64.AppImage
+echo "Built dist/SaraView-x86_64.AppImage"