Build all apps from Markdown content; Compose Desktop replaces GTK on Linux and Windows

- content/ + scripts/build-content.py produce content.json for every app
- stable lesson IDs with one-time progress migration (Swift, Kotlin)
- shared answer-check tests (tests/answers.json) for Kotlin and Swift
- android/desktop: Compose app with updater, speech and GTK progress import
- CI packages AppImage and Windows zip with ProGuard, runs the tests

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/bundle-windows.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+# Windows x64 zip of the Compose desktop app, with its own Java runtime.
+# Runs in Git Bash or MSYS2. Needs python3 and a JDK 17+ that ships jmods
+# (set PACKAGE_JDK, e.g. Temurin 21).
+#
+# graduately.exe must sit at the root of the zip: the installer and the
+# updater of older builds unpack it over the install folder and start it.
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+cd "$ROOT"
+
+OUT="$ROOT/dist/graduately-windows-x64.zip"
+IMAGE="$ROOT/android/desktop/build/compose/binaries/main-release/app/graduately"
+
+echo "==> Building the desktop app"
+(cd android && ./gradlew :desktop:createReleaseDistributable --no-daemon)
+
+[[ -f "$IMAGE/graduately.exe" ]] || { echo "graduately.exe missing in $IMAGE" >&2; exit 1; }
+
+echo "==> Zipping"
+mkdir -p "$ROOT/dist"
+rm -f "$OUT"
+if command -v 7z >/dev/null 2>&1; then
+  (cd "$IMAGE" && 7z a -tzip -mx=9 "$OUT" . >/dev/null)
+else
+  powershell -NoProfile -Command "Compress-Archive -Path '$(cygpath -w "$IMAGE")\\*' -DestinationPath '$(cygpath -w "$OUT")'"
+fi
+echo "Created ${OUT#"$ROOT"/}"