refactor: Projektstruktur in app/ und backend/ aufgeteilt

backend/types.d.ts

@@ -0,0 +1,17 @@
+// This TypeScript modules definition file is generated by vaadin-maven-plugin.
+// You can not directly import your different static files into TypeScript,
+// This is needed for TypeScript compiler to declare and export as a TypeScript module.
+// It is recommended to commit this file to the VCS.
+// You might want to change the configurations to fit your preferences
+declare module '*.css?inline' {
+  import type { CSSResultGroup } from 'lit';
+  const content: CSSResultGroup;
+  export default content;
+}
+
+// Allow any CSS Custom Properties
+declare module 'csstype' {
+  interface Properties {
+    [index: `--${string}`]: any;
+  }
+}