feat(profile): advertise per-variant dictionary versions for offline preload

The Profile now carries dict_versions (game variant -> current dictionary
version), populated from the dictionary registry at the profileResponse
choke point, so an installed PWA can preload the matching dawg per enabled
variant off the existing cold-start profile request instead of adding a
round-trip for a rare feature.

Wire path: FBS DictVersion table + Profile.dict_versions (additive,
backward-compatible trailing field) -> backend dto/registry -> gateway
ProfileResp + FBS encoder -> client codec decode into a per-variant map on
model.Profile. Empty in a degenerate no-dictionary deployment; the mock
serves v1.3.0 for all three variants. Codec decode covered by a
bite-tested round-trip unit test.

pkg/fbs/scrabblefb/Profile.go

@@ -211,8 +211,28 @@ func (rcv *Profile) MutateVkLinked(n bool) bool {
 	return rcv._tab.MutateBoolSlot(34, n)
 }
 
+func (rcv *Profile) DictVersions(obj *DictVersion, j int) bool {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(36))
+	if o != 0 {
+		x := rcv._tab.Vector(o)
+		x += flatbuffers.UOffsetT(j) * 4
+		x = rcv._tab.Indirect(x)
+		obj.Init(rcv._tab.Bytes, x)
+		return true
+	}
+	return false
+}
+
+func (rcv *Profile) DictVersionsLength() int {
+	o := flatbuffers.UOffsetT(rcv._tab.Offset(36))
+	if o != 0 {
+		return rcv._tab.VectorLen(o)
+	}
+	return 0
+}
+
 func ProfileStart(builder *flatbuffers.Builder) {
-	builder.StartObject(16)
+	builder.StartObject(17)
 }
 func ProfileAddUserId(builder *flatbuffers.Builder, userId flatbuffers.UOffsetT) {
 	builder.PrependUOffsetTSlot(0, flatbuffers.UOffsetT(userId), 0)
@@ -265,6 +285,12 @@ func ProfileAddTelegramLinked(builder *flatbuffers.Builder, telegramLinked bool)
 func ProfileAddVkLinked(builder *flatbuffers.Builder, vkLinked bool) {
 	builder.PrependBoolSlot(15, vkLinked, false)
 }
+func ProfileAddDictVersions(builder *flatbuffers.Builder, dictVersions flatbuffers.UOffsetT) {
+	builder.PrependUOffsetTSlot(16, flatbuffers.UOffsetT(dictVersions), 0)
+}
+func ProfileStartDictVersionsVector(builder *flatbuffers.Builder, numElems int) flatbuffers.UOffsetT {
+	return builder.StartVector(4, numElems, 4)
+}
 func ProfileEnd(builder *flatbuffers.Builder) flatbuffers.UOffsetT {
 	return builder.EndObject()
 }