Panic on non-numeric score ID in pin/unpin handlers

[raya-ac]

ScoresPinAddPOST and ScoresPinDelPOST call strconv.ParseInt on user-supplied score IDs and panic(err) on failure. Any authenticated user can crash the handler by sending a non-numeric ID.

app/v1/user_scores.go, lines 183-186 and 203-206