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/2-rocnik/03-prvni-brigada.md

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+---
+id: anglictina-2-prvni-brigada
+puvodni: en.2.3
+nazev: První brigáda
+popis: Předpřítomný čas, for a since. Poslech pohovoru a doplňování.
+---
+
+# Výklad
+
+## Zkušenost a děj až do teď
+*Present perfect*
+
+- I have worked in a café. She has never had a paid job.
+- Ever v otázce, never v záporném významu: Have you ever used a till?
+- For three months = jak dlouho. Since May = od kdy.
+- Just, already, yet: I've just finished. I haven't finished yet.
+
+> Tip: have/has + příčestí. Otázka na zkušenost začíná Have you ever…?
+
+## Krátké odpovědi
+*Pohovor*
+
+- I'm reliable and I get on well with people.
+- I have looked after my neighbours' children.
+- I can work on Saturdays, but I can't work on Sunday mornings.
+- Could you tell me what the shift is?
+
+> Tip: odpovězte a přidejte jednu konkrétní větu, ať to není jen yes.
+
+
+# Poslech
+
+Manager: Have you ever worked in a shop? Tereza: Not in a shop, but I have helped in my uncle's bakery since May. Manager: What do you do there? Tereza: I have served customers and I have learned to use the till. I haven't baked bread yet. Manager: Can you start next Saturday? Tereza: Yes. I have already asked my uncle, and he says it's fine. I can't work on Sunday mornings because I have a match.
+
+## Where has Tereza helped?
+- In a supermarket
+- [x] In her uncle's bakery
+- In a hotel
+- At school
+> in my uncle's bakery.
+
+## Since when?
+- Since March
+- [x] Since May
+- Since Saturday
+- For a year
+> since May.
+
+## What hasn't she done yet?
+- Served customers
+- Used the till
+- [x] Baked bread
+- Asked her uncle
+> I haven't baked bread yet.
+
+## Why can't she work on Sunday mornings?
+- The bakery is closed
+- [x] She has a match
+- She is ill
+- She has no till
+> because I have a match.
+
+
+# Doplňování
+
+## She ___ (live) here since 2019.
+= has lived|'s lived
+> Since + předpřítomný čas.
+
+## I have known him ___ three years.
+= for
+> For + délka.
+
+## Have you ___ (be) to London?
+= been
+> Been to = mít zkušenost.
+
+## We haven't finished ___.
+= yet
+> Yet v záporu na konci.
+
+## He has ___ eaten, so he isn't hungry.
+= already|just
+> Already nebo just.