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>

content/anglictina/3-rocnik/04-pro-a-proti.md

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+---
+id: anglictina-3-pro-a-proti
+puvodni: en.3.4
+nazev: Pro a proti
+popis: Stavba úvahy a spojovací výrazy. Esej a kvíz.
+---
+
+# Výklad
+
+## Úvod, dvě strany, závěr
+*Čtyři kroky*
+
+- Úvod: o čem text je a že existují dva pohledy.
+- Jeden odstavec pro výhody, jeden pro nevýhody.
+- On the one hand … On the other hand …
+- Závěr: váš názor. In my opinion, I believe. Nepřidávejte úplně nový argument.
+
+> Tip: v úvodu otázku neopakujte doslova. Převeďte ji vlastními slovy.
+
+## However není because
+*Spojky*
+
+- School uniforms are cheaper. However, they limit personality.
+- Although uniforms save time, many students hate them.
+- Because dává důvod. So dává výsledek.
+- In conclusion shrnuje. Nepíše se In the conclusion.
+
+> Tip: however stojí mezi větami a odděluje se čárkou. Although spojuje věty v jednu.
+
+
+# Psaní
+
+Write a for-and-against paragraph of at least 50 words about school uniforms. Use however and because, and finish with your opinion using believe.
+
+## Vzorová odpověď
+
+School uniforms are a common argument. They are practical because students do not have to decide what to wear, and families spend less money. However, a uniform hides personality and can feel childish at eighteen. Although it makes mornings faster, it does not make lessons better. I believe schools should keep a simple dress code, but they should not force one jacket on everyone.
+
+## Musí obsahovat
+
+- however
+- because
+- believe
+
+## Minimum slov
+
+50
+
+
+# Kvíz
+
+## Which linker shows contrast?
+- because
+- [x] however
+- so
+- for example
+> However staví protiklad.
+
+## ___ uniforms save time, students still complain.
+- However
+- [x] Although
+- So
+- Believe
+> Although spojuje dvě části jedné věty.
+
+## Choose the best ending of an essay.
+- In conclusion, I have no idea.
+- [x] In conclusion, I believe a simple rule is enough.
+- Because however so.
+- To begin with, the essay starts now.
+> Závěr má názor, ne nový zmatek.
+
+## Because introduces…
+- a result only
+- [x] a reason
+- a list of names
+- a question
+> Because = důvod.