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.

ui/src/lib/model.ts

@@ -156,6 +156,11 @@ export interface Profile {
   variantPreferences: Variant[];
   /** The advertising-banner block, present only for a viewer eligible to see it. */
   banner?: Banner;
+  /** The account's confirmed email address ("" when none). */
+  email: string;
+  /** Whether a Telegram / VK identity is attached — drives the Add / Unlink controls. */
+  telegramLinked: boolean;
+  vkLinked: boolean;
 }
 
 /** Banner is the advertising-banner block of an eligible viewer's profile. */