Change discordId type from integer to string across frontend, backend, and API schema for consistency and proper validation.

backend/src/main/java/com/alttd/altitudeweb/mappers/BannedUserToBannedUserDtoMapper.java

@@ -8,7 +8,7 @@ import org.springframework.stereotype.Service;
 public class BannedUserToBannedUserDtoMapper {
 
     public BannedUserDto map(BannedUser bannedUser) {
-        return new BannedUserDto(bannedUser.userId(), bannedUser.reason(), bannedUser.name(), bannedUser.avatarUrl());
+        return new BannedUserDto(String.valueOf(bannedUser.userId()), bannedUser.reason(), bannedUser.name(), bannedUser.avatarUrl());
     }
 
 }

backend/src/main/java/com/alttd/altitudeweb/mappers/DiscordAppealDtoToDiscordAppealMapper.java

@@ -14,7 +14,7 @@ public class DiscordAppealDtoToDiscordAppealMapper {
         return new DiscordAppeal(
                 UUID.randomUUID(),
                 loggedInUserUuid,
-                discordAppealDto.getDiscordId(),
+                Long.parseLong(discordAppealDto.getDiscordId()),
                 discordUsername,
                 discordAppealDto.getAppeal(),
                 Instant.now(),