Hide clan tags in public FFA games to prevent teaming (#4000)

## Description:

- Added optional `disableClanTags` to `GameConfig`. When set, the server
strips clan tags from `gameInfo` (lobby broadcasts/HTTP) and
`gameStartInfo` (start payload) before sending to clients. Archive keeps
the originals.
- Enabled `disableClanTags` for public FFA games (both the regular FFA
playlist and special when randomized to FFA). No UI; clients still see
their own clan tag via local input state.

## 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:

evan

src/core/Schemas.ts

@@ -253,6 +253,7 @@ export const GameConfigSchema = z.object({
   instantBuild: z.boolean(),
   disableNavMesh: z.boolean().optional(),
   disableAlliances: z.boolean().nullable().optional(),
+  disableClanTags: z.boolean().optional(),
   waterNukes: z.boolean().nullable().optional(),
   randomSpawn: z.boolean(),
   maxPlayers: z.number().optional(),