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).

gateway/internal/transcode/encode.go

@@ -81,6 +81,20 @@ func encodeProfile(p backendclient.ProfileResp) []byte {
 	return b.FinishedBytes()
 }
 
+// encodeBlockStatus builds a BlockStatus payload.
+func encodeBlockStatus(s backendclient.BlockStatusResp) []byte {
+	b := flatbuffers.NewBuilder(128)
+	until := b.CreateString(s.Until)
+	reason := b.CreateString(s.Reason)
+	fb.BlockStatusStart(b)
+	fb.BlockStatusAddBlocked(b, s.Blocked)
+	fb.BlockStatusAddPermanent(b, s.Permanent)
+	fb.BlockStatusAddUntil(b, until)
+	fb.BlockStatusAddReason(b, reason)
+	b.Finish(fb.BlockStatusEnd(b))
+	return b.FinishedBytes()
+}
+
 // encodeLinkResult builds a LinkResult payload. A switched-session token
 // (a guest initiator whose durable counterpart won) is carried as a nested Session
 // for the client to adopt; it is omitted otherwise. supportedLangs is the variant