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/test-answers-swift.sh

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+# Shared answer-check cases (tests/answers.json) against the Swift apps' code.
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd)"
+OUT="$ROOT/build/tests"
+mkdir -p "$OUT"
+
+python3 "$ROOT/scripts/build-content.py" --out "$OUT/content.json"
+xcrun swiftc -O -o "$OUT/swift-answers" \
+  "$ROOT/ios/Graduately/Data/Answers.swift" "$ROOT/tests/swift/main.swift"
+"$OUT/swift-answers" "$ROOT/tests/answers.json" "$OUT/content.json"