Desktop app dynamic config of API Port (#40)

* added dynamic configuration of Port in Desktop app
* added dynamic configuration of API_URL to docker deployments.

Now it works with editing only .env file.

frontend/wailsjs/go/main/App.d.ts

@@ -0,0 +1,4 @@
+// Cynhyrchwyd y ffeil hon yn awtomatig. PEIDIWCH Â MODIWL
+// This file is automatically generated. DO NOT EDIT
+
+export function GetAPIBaseURL():Promise<string>;