feat(profile): carry linked identities in the profile (email, telegram, vk)

Add email / telegram_linked / vk_linked to the Profile (fbs table + regenerated
Go/TS bindings, gateway ProfileResp + encodeProfile, backend DTO, UI model +
decode). They are filled outside the pure projection — Server.profileResponse now
reads the account's identities (like the banner seam) — and will drive the profile's
Add / Unlink / change-email controls.

pkg/fbs/scrabble.fbs

@@ -224,6 +224,12 @@ table Profile {
   // variant_preferences is the set of game variants the player allows themselves to be
   // matched into (engine.Variant labels), Erudit-first; the New Game picker is gated by it.
   variant_preferences:[string];
+  // email is the account's confirmed email address ("" when none); telegram_linked and
+  // vk_linked report whether a platform identity is attached. They drive the profile's
+  // link / unlink / change-email controls (all added trailing — backward-compatible).
+  email:string;
+  telegram_linked:bool;
+  vk_linked:bool;
 }
 
 // BlockStatus reports the caller's current manual block. The UI fetches it after any operation