style: remove hyphens from compound adjectives in comments and messages

Remove hyphens from compound adjectives such as "logged-in", "one-time", "password-protected", "full-height", "multi-file", and "S3-compatible" in comments, test error messages, and UI labels to improve readability and consistency.

backend/libs/handlers/api_docs.go

@@ -59,7 +59,7 @@ func (a *App) ShareXAnonymousConfig(w http.ResponseWriter, r *http.Request) {
 		"RequestURL":      a.cfg.BaseURL + "/api/v1/upload",
 		"Headers": map[string]string{
 			"Accept": "application/json",
-			// Group a multi-file selection (sent as back-to-back requests) into
+			// Group a multiple file selection (sent as back to back requests) into
 			// one box. Remove this header for one box per file.
 			uploadBatchHeader: "sharex",
 		},