Stage 8: UI social/account/history surfaces

Wire the deferred Stage 7 surfaces end-to-end (UI -> gateway transcode ->
backend REST -> existing domain services): friends (incl. one-time friend
codes), per-user blocks, friend-game invitations, profile editing + email
binding, the statistics screen, and the in-game history + GCG export.

Friends gain two add paths (interview decision, a deliberate plan change):
one-time 6-digit codes (friend_codes table, 12h TTL, single-use, rate-limited
redeem); and play-gated requests (shared game required) where an explicit
decline is permanent, an ignored request lapses after 30 days, and a code
bypasses a decline. Migration 00006 widens friendships_status_chk and adds
friend_codes.

Lobby notification badge is poll + push: a new generic `notify` event drives
it live; the client polls on open/focus. Language stays a single Settings
control that writes through to the durable account's preferred_language. GCG
export is finished-only (game.ErrGameActive) and shares/downloads the .gcg file.

Tests: backend unit + inttest (friend gate/decline/code, ListInvitations,
GetStats, GCG gate), gateway transcode round-trips + notify constructor, UI
vitest (codecs, win-rate, share choice) + Playwright social specs. Docs: PLAN
(Stage 8 done + refinements + TODO-5), ARCHITECTURE, FUNCTIONAL(+ru), UI_DESIGN,
TESTING, module READMEs.

pkg/fbs/scrabblefb/Profile.go

@@ -121,8 +121,24 @@ func (rcv *Profile) MutateIsGuest(n bool) bool {
 	return rcv._tab.MutateBoolSlot(18, n)
 }
 
+func (rcv *Profile) AwayStart() []byte {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(20))
+	if o != 0 {
+		return rcv._tab.ByteVector(o + rcv._tab.Pos)
+	}
+	return nil
+}
+
+func (rcv *Profile) AwayEnd() []byte {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(22))
+	if o != 0 {
+		return rcv._tab.ByteVector(o + rcv._tab.Pos)
+	}
+	return nil
+}
+
 func ProfileStart(builder *flatbuffers.Builder) {
-	builder.StartObject(8)
+	builder.StartObject(10)
 }
 func ProfileAddUserId(builder *flatbuffers.Builder, userId flatbuffers.UOffsetT) {
 	builder.PrependUOffsetTSlot(0, flatbuffers.UOffsetT(userId), 0)
@@ -148,6 +164,12 @@ func ProfileAddBlockFriendRequests(builder *flatbuffers.Builder, blockFriendRequ
 func ProfileAddIsGuest(builder *flatbuffers.Builder, isGuest bool) {
 	builder.PrependBoolSlot(7, isGuest, false)
 }
+func ProfileAddAwayStart(builder *flatbuffers.Builder, awayStart flatbuffers.UOffsetT) {
+	builder.PrependUOffsetTSlot(8, flatbuffers.UOffsetT(awayStart), 0)
+}
+func ProfileAddAwayEnd(builder *flatbuffers.Builder, awayEnd flatbuffers.UOffsetT) {
+	builder.PrependUOffsetTSlot(9, flatbuffers.UOffsetT(awayEnd), 0)
+}
 func ProfileEnd(builder *flatbuffers.Builder) flatbuffers.UOffsetT {
 	return builder.EndObject()
 }