feat(admin): manual account blocking (suspensions)

Operator-driven hard block, the counterpart to the soft high-rate flag: permanent or until a date, with an optional reason chosen from an editable en+ru picklist (snapshotted onto the block). A block forfeits the player's active games (opponent wins, as a resignation) and cancels their open matchmaking games. A backend gate refuses a blocked account on every /api/v1/user/* route except the block-status probe with 403 account_blocked, which threads through the gateway as the Execute result_code; the UI surfaces it as a terminal blocked screen and stops all push/poll. Temporary blocks self-expire; the operator can unblock at any time (lost games stay lost). Sessions are not revoked, so the blocked client can still reach the exempt block-status endpoint.

Backend: migration 00003 (account_suspensions + suspension_reasons) + jet regen; account suspension store; game.ForfeitAllForAccount; requireNotSuspended gate + block-status endpoint; admin console block/unblock + Reasons CRUD. Wire: fbs BlockStatus + account.block_status gateway op. UI: blocked screen, app state, transport/codec, i18n. Docs: ARCHITECTURE, FUNCTIONAL(+ru), PRERELEASE (AB).

pkg/fbs/scrabble.fbs

@@ -150,6 +150,18 @@ table Profile {
   notifications_in_app_only:bool = true;
 }
 
+// BlockStatus reports the caller's current manual block. The UI fetches it after any operation
+// returns the "account_blocked" result code, then replaces every screen with the terminal blocked
+// screen and stops all push/poll. permanent is false for a temporary block; until is an RFC3339
+// UTC instant for a temporary block and empty for a permanent one; reason is the operator-set text
+// resolved to the account's language, empty when none was cited.
+table BlockStatus {
+  blocked:bool;
+  permanent:bool;
+  until:string;
+  reason:string;
+}
+
 // --- game (authenticated) ---
 
 // SubmitPlayRequest places tiles on the player's turn; the backend infers the play's