fix(errors): align 204 copy and validate axios error titles

Use "No content." for status 204. Only set the toast message from
response.data.title when it is a non-empty string so the generic
message is preserved when title is missing or empty.

src/lib/handle-server-error.ts

@@ -15,11 +15,14 @@ export function handleServerError(error: unknown) {
     'status' in error &&
     Number(error.status) === 204
   ) {
-    errMsg = 'Content not found.'
+    errMsg = 'No content.'
   }
 
   if (error instanceof AxiosError) {
-    errMsg = error.response?.data.title
+    const title = error.response?.data?.title
+    if (typeof title === 'string' && title.length > 0) {
+      errMsg = title
+    }
   }
 
   toast.error(errMsg)