Syntax fixes (#5367)

* Declare return types on functions

And a very few other type related minor fixes

* Minor syntax fixes

* Remove unnecessary escape chars in regexes
* Remove unnecessary awaits
* Replace deprecated req.connection with req.socket
* Replace deprecated upload with uploadOne
* Remove unnecessary eslint-disable-next-line comments
* Comment empty functions / catch or finally clauses
* Fix irregular whitespaces
* Add missing returns (null)
* Remove unreachable code
* A few logical fixes
* Remove / Handle non-null assertions which are certainly unnecessary (e.g. in
tests)

app/src/utils/unexpected-error.ts

@@ -5,7 +5,7 @@ import { APIError } from '@/types';
 
 let store: any;
 
-export function unexpectedError(error: Error | RequestError | APIError) {
+export function unexpectedError(error: Error | RequestError | APIError): void {
 	if (!store) store = useNotificationsStore();
 
 	const code =