Clan System Part 1 (#3276)

## Description:

Properly split out clantags and usernames, a clantag should not be part
of a username.

<img width="285" height="286" alt="image"
src="https://github.com/user-attachments/assets/8ac56e82-b12c-4fc0-9774-e445252a6e61"
/>

https://api.openfront.dev/game/ojkqZFb2


<img width="296" height="596" alt="image"
src="https://github.com/user-attachments/assets/85152f80-c111-4f87-b85b-8516c9c6137b"
/>


https://api.openfront.dev/game/MF32BkVc


requires;
https://github.com/openfrontio/infra/pull/264

## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

## Please put your Discord username so you can be contacted if a bug or
regression is found:

w.o.n

src/core/validations/username.ts

@@ -1,8 +1,10 @@
 import { translateText } from "../../client/Utils";
-import { UsernameSchema } from "../Schemas";
+import { ClanTagSchema, UsernameSchema } from "../Schemas";
 
 export const MIN_USERNAME_LENGTH = 3;
 export const MAX_USERNAME_LENGTH = 27;
+export const MIN_CLAN_TAG_LENGTH = 2;
+export const MAX_CLAN_TAG_LENGTH = 5;
 
 export function validateUsername(username: string): {
   isValid: boolean;
@@ -44,3 +46,28 @@ export function validateUsername(username: string): {
   // All checks passed
   return { isValid: true };
 }
+
+export function validateClanTag(clanTag: string): {
+  isValid: boolean;
+  error?: string;
+} {
+  if (clanTag.length === 0) {
+    return { isValid: true };
+  }
+  if (clanTag.length < MIN_CLAN_TAG_LENGTH) {
+    return { isValid: false, error: translateText("username.tag_too_short") };
+  }
+  if (clanTag.length > MAX_CLAN_TAG_LENGTH) {
+    return { isValid: false, error: translateText("username.tag_too_short") };
+  }
+
+  const parsed = ClanTagSchema.safeParse(clanTag);
+  if (!parsed.success) {
+    return {
+      isValid: false,
+      error: translateText("username.tag_invalid_chars"),
+    };
+  }
+
+  return { isValid: true };
+}