chore: Version 0.9.21, Android-Build-Tooling und Flutter-Abhängigkeiten aktualisiert

- Version auf 0.9.21 angehoben (App und Backend)
- Gradle 8.14.3, AGP 8.11.1, Kotlin 2.2.20; Flutter-Migrator-Flags in gradle.properties
- camera ^0.12.0, mobile_scanner ^7.0.0
- tsconfig ignoreDeprecations auf 5.0, prod.bundle neu gebaut
- upload.sh entfernt

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

app/android/settings.gradle.kts

@@ -18,8 +18,8 @@ pluginManagement {
 
 plugins {
     id("dev.flutter.flutter-plugin-loader") version "1.0.0"
-    id("com.android.application") version "8.7.0" apply false
-    id("org.jetbrains.kotlin.android") version "2.1.0" apply false
+    id("com.android.application") version "8.11.1" apply false
+    id("org.jetbrains.kotlin.android") version "2.2.20" apply false
 }
 
 include(":app")