refactor: move app to monorepo

frontend/app/PITFALLS.md

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+# Pitfalls
+
+This file is used to document problems, that occurred during development and how to fix them.
+
+## Ionic Framework
+
+### Build platform Android
+
+#### Problem
+
+After calling `ionic cordova build android` the gradle version is not set correctly (4.1 instead of 4.6)
+
+#### Solution
+
+- Go to folder `APP_FOLDER/platforms/android/cordova/lib/builders/`
+- Open file `GradleBuilder.js` and change gradle version to `gradle-4.6-all.zip`
+  in line `var distributionUrl = process.env['CORDOVA_ANDROID_GRADLE_DISTRIBUTION_URL'] || 'https\\://services.gradle.org/distributions/gradle-4.1-all.zip';`
+- Repeat this for file `StudioBuilder.js`
+
+#### Problem
+
+`android.support... not found` on build
+
+#### Solution
+
+```
+npm install jetifier
+npx jetify
+npx cap sync android
+```
+
+[more here](https://stackoverflow.com/questions/62195760/ionic-capacitor-build-cannot-find-symbol-android-support-v4-app-activitycompat)
+
+### Run platform iOS
+
+#### Problem
+
+Currently, the iOS project build with cordova uses the old build system.
+The command `ionic cordova run ios` runs into the error `/platforms/ios/build/emulator/StApps.app/Info.plist file not found.`
+
+#### Solution
+
+- Either use the command: `ionic cordova emulate ios -- --buildFlag="-UseModernBuildSystem=0"`
+- Or open the iOS project in Xcode and change build system in workspace settings to `Lagacy Build System`. Then the normal run command works also.